closure-builder/third_party/closure-library/closure/goog/base.js

Simple Closure, Soy and JavaScript Build system

// Copyright 2006 The Closure Library Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS-IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

/**
 * @fileoverview Bootstrap for the Google JS Library (Closure).
 *
 * In uncompiled mode base.js will attempt to load Closure's deps file, unless
 * the global <code>CLOSURE_NO_DEPS</code> is set to true.  This allows projects
 * to include their own deps file(s) from different locations.
 *
 * Avoid including base.js more than once. This is strictly discouraged and not
 * supported. goog.require(...) won't work properly in that case.
 *
 * @provideGoog
 */


/**
 * @define {boolean} Overridden to true by the compiler.
 */
var COMPILED = false;


/**
 * Base namespace for the Closure library.  Checks to see goog is already
 * defined in the current scope before assigning to prevent clobbering if
 * base.js is loaded more than once.
 *
 * @const
 */
var goog = goog || {};

/**
 * Reference to the global context.  In most cases this will be 'window'.
 * @const
 * @suppress {newCheckTypes}
 */
goog.global = this;


/**
 * A hook for overriding the define values in uncompiled mode.
 *
 * In uncompiled mode, `CLOSURE_UNCOMPILED_DEFINES` may be defined before
 * loading base.js.  If a key is defined in `CLOSURE_UNCOMPILED_DEFINES`,
 * `goog.define` will use the value instead of the default value.  This
 * allows flags to be overwritten without compilation (this is normally
 * accomplished with the compiler's "define" flag).
 *
 * Example:
 * <pre>
 *   var CLOSURE_UNCOMPILED_DEFINES = {'goog.DEBUG': false};
 * </pre>
 *
 * @type {Object<string, (string|number|boolean)>|undefined}
 */
goog.global.CLOSURE_UNCOMPILED_DEFINES;


/**
 * A hook for overriding the define values in uncompiled or compiled mode,
 * like CLOSURE_UNCOMPILED_DEFINES but effective in compiled code.  In
 * uncompiled code CLOSURE_UNCOMPILED_DEFINES takes precedence.
 *
 * Also unlike CLOSURE_UNCOMPILED_DEFINES the values must be number, boolean or
 * string literals or the compiler will emit an error.
 *
 * While any @define value may be set, only those set with goog.define will be
 * effective for uncompiled code.
 *
 * Example:
 * <pre>
 *   var CLOSURE_DEFINES = {'goog.DEBUG': false} ;
 * </pre>
 *
 * @type {Object<string, (string|number|boolean)>|undefined}
 */
goog.global.CLOSURE_DEFINES;


/**
 * Returns true if the specified value is not undefined.
 *
 * @param {?} val Variable to test.
 * @return {boolean} Whether variable is defined.
 */
goog.isDef = function(val) {
  // void 0 always evaluates to undefined and hence we do not need to depend on
  // the definition of the global variable named 'undefined'.
  return val !== void 0;
};

/**
 * Returns true if the specified value is a string.
 * @param {?} val Variable to test.
 * @return {boolean} Whether variable is a string.
 */
goog.isString = function(val) {
  return typeof val == 'string';
};


/**
 * Returns true if the specified value is a boolean.
 * @param {?} val Variable to test.
 * @return {boolean} Whether variable is boolean.
 */
goog.isBoolean = function(val) {
  return typeof val == 'boolean';
};


/**
 * Returns true if the specified value is a number.
 * @param {?} val Variable to test.
 * @return {boolean} Whether variable is a number.
 */
goog.isNumber = function(val) {
  return typeof val == 'number';
};


/**
 * Builds an object structure for the provided namespace path, ensuring that
 * names that already exist are not overwritten. For example:
 * "a.b.c" -> a = {};a.b={};a.b.c={};
 * Used by goog.provide and goog.exportSymbol.
 * @param {string} name name of the object that this file defines.
 * @param {*=} opt_object the object to expose at the end of the path.
 * @param {Object=} opt_objectToExportTo The object to add the path to; default
 *     is `goog.global`.
 * @private
 */
goog.exportPath_ = function(name, opt_object, opt_objectToExportTo) {
  var parts = name.split('.');
  var cur = opt_objectToExportTo || goog.global;

  // Internet Explorer exhibits strange behavior when throwing errors from
  // methods externed in this manner.  See the testExportSymbolExceptions in
  // base_test.html for an example.
  if (!(parts[0] in cur) && typeof cur.execScript != 'undefined') {
    cur.execScript('var ' + parts[0]);
  }

  for (var part; parts.length && (part = parts.shift());) {
    if (!parts.length && goog.isDef(opt_object)) {
      // last part and we have an object; use it
      cur[part] = opt_object;
    } else if (cur[part] && cur[part] !== Object.prototype[part]) {
      cur = cur[part];
    } else {
      cur = cur[part] = {};
    }
  }
};


/**
 * Defines a named value. In uncompiled mode, the value is retrieved from
 * CLOSURE_DEFINES or CLOSURE_UNCOMPILED_DEFINES if the object is defined and
 * has the property specified, and otherwise used the defined defaultValue.
 * When compiled the default can be overridden using the compiler options or the
 * value set in the CLOSURE_DEFINES object. Returns the defined value so that it
 * can be used safely in modules. Note that the value type MUST be either
 * boolean, number, or string.
 *
 * @param {string} name The distinguished name to provide.
 * @param {T} defaultValue
 * @return {T} The defined value.
 * @template T
 */
goog.define = function(name, defaultValue) {
  var value = defaultValue;
  if (!COMPILED) {
    var uncompiledDefines = goog.global.CLOSURE_UNCOMPILED_DEFINES;
    var defines = goog.global.CLOSURE_DEFINES;
    if (uncompiledDefines &&
        // Anti DOM-clobbering runtime check (b/37736576).
        /** @type {?} */ (uncompiledDefines).nodeType === undefined &&
        Object.prototype.hasOwnProperty.call(uncompiledDefines, name)) {
      value = uncompiledDefines[name];
    } else if (
        defines &&
        // Anti DOM-clobbering runtime check (b/37736576).
        /** @type {?} */ (defines).nodeType === undefined &&
        Object.prototype.hasOwnProperty.call(defines, name)) {
      value = defines[name];
    }
  }
  goog.exportPath_(name, value);
  return value;
};


/**
 * @define {number} Integer year indicating the set of browser features that are
 * guaranteed to be present.  This is defined to include exactly features that
 * work correctly on all "modern" browsers that are stable on January 1 of the
 * specified year.  For example,
 * ```js
 * if (goog.FEATURESET_YEAR >= 2019) {
 *   // use APIs known to be available on all major stable browsers Jan 1, 2019
 * } else {
 *   // polyfill for older browsers
 * }
 * ```
 * This is intended to be the primary define for removing
 * unnecessary browser compatibility code (such as ponyfills and workarounds),
 * and should inform the default value for most other defines:
 * ```js
 * const ASSUME_NATIVE_PROMISE =
 *     goog.define('ASSUME_NATIVE_PROMISE', goog.FEATURESET_YEAR >= 2016);
 * ```
 *
 * The default assumption is that IE9 is the lowest supported browser, which was
 * first available Jan 1, 2012.
 *
 * TODO(user): Reference more thorough documentation when it's available.
 */
goog.FEATURESET_YEAR = goog.define('goog.FEATURESET_YEAR', 2012);


/**
 * @define {boolean} DEBUG is provided as a convenience so that debugging code
 * that should not be included in a production. It can be easily stripped
 * by specifying --define goog.DEBUG=false to the Closure Compiler aka
 * JSCompiler. For example, most toString() methods should be declared inside an
 * "if (goog.DEBUG)" conditional because they are generally used for debugging
 * purposes and it is difficult for the JSCompiler to statically determine
 * whether they are used.
 */
goog.DEBUG = goog.define('goog.DEBUG', true);


/**
 * @define {string} LOCALE defines the locale being used for compilation. It is
 * used to select locale specific data to be compiled in js binary. BUILD rule
 * can specify this value by "--define goog.LOCALE=<locale_name>" as a compiler
 * option.
 *
 * Take into account that the locale code format is important. You should use
 * the canonical Unicode format with hyphen as a delimiter. Language must be
 * lowercase, Language Script - Capitalized, Region - UPPERCASE.
 * There are few examples: pt-BR, en, en-US, sr-Latin-BO, zh-Hans-CN.
 *
 * See more info about locale codes here:
 * http://www.unicode.org/reports/tr35/#Unicode_Language_and_Locale_Identifiers
 *
 * For language codes you should use values defined by ISO 693-1. See it here
 * http://www.w3.org/WAI/ER/IG/ert/iso639.htm. There is only one exception from
 * this rule: the Hebrew language. For legacy reasons the old code (iw) should
 * be used instead of the new code (he).
 *
 */
goog.LOCALE = goog.define('goog.LOCALE', 'en');  // default to en


/**
 * @define {boolean} Whether this code is running on trusted sites.
 *
 * On untrusted sites, several native functions can be defined or overridden by
 * external libraries like Prototype, Datejs, and JQuery and setting this flag
 * to false forces closure to use its own implementations when possible.
 *
 * If your JavaScript can be loaded by a third party site and you are wary about
 * relying on non-standard implementations, specify
 * "--define goog.TRUSTED_SITE=false" to the compiler.
 */
goog.TRUSTED_SITE = goog.define('goog.TRUSTED_SITE', true);


/**
 * @define {boolean} Whether a project is expected to be running in strict mode.
 *
 * This define can be used to trigger alternate implementations compatible with
 * running in EcmaScript Strict mode or warn about unavailable functionality.
 * @see https://goo.gl/PudQ4y
 *
 */
goog.STRICT_MODE_COMPATIBLE = goog.define('goog.STRICT_MODE_COMPATIBLE', false);


/**
 * @define {boolean} Whether code that calls {@link goog.setTestOnly} should
 *     be disallowed in the compilation unit.
 */
goog.DISALLOW_TEST_ONLY_CODE =
    goog.define('goog.DISALLOW_TEST_ONLY_CODE', COMPILED && !goog.DEBUG);


/**
 * @define {boolean} Whether to use a Chrome app CSP-compliant method for
 *     loading scripts via goog.require. @see appendScriptSrcNode_.
 */
goog.ENABLE_CHROME_APP_SAFE_SCRIPT_LOADING =
    goog.define('goog.ENABLE_CHROME_APP_SAFE_SCRIPT_LOADING', false);


/**
 * Defines a namespace in Closure.
 *
 * A namespace may only be defined once in a codebase. It may be defined using
 * goog.provide() or goog.module().
 *
 * The presence of one or more goog.provide() calls in a file indicates
 * that the file defines the given objects/namespaces.
 * Provided symbols must not be null or undefined.
 *
 * In addition, goog.provide() creates the object stubs for a namespace
 * (for example, goog.provide("goog.foo.bar") will create the object
 * goog.foo.bar if it does not already exist).
 *
 * Build tools also scan for provide/require/module statements
 * to discern dependencies, build dependency files (see deps.js), etc.
 *
 * @see goog.require
 * @see goog.module
 * @param {string} name Namespace provided by this file in the form
 *     "goog.package.part".
 */
goog.provide = function(name) {
  if (goog.isInModuleLoader_()) {
    throw new Error('goog.provide cannot be used within a module.');
  }
  if (!COMPILED) {
    // Ensure that the same namespace isn't provided twice.
    // A goog.module/goog.provide maps a goog.require to a specific file
    if (goog.isProvided_(name)) {
      throw new Error('Namespace "' + name + '" already declared.');
    }
  }

  goog.constructNamespace_(name);
};


/**
 * @param {string} name Namespace provided by this file in the form
 *     "goog.package.part".
 * @param {Object=} opt_obj The object to embed in the namespace.
 * @private
 */
goog.constructNamespace_ = function(name, opt_obj) {
  if (!COMPILED) {
    delete goog.implicitNamespaces_[name];

    var namespace = name;
    while ((namespace = namespace.substring(0, namespace.lastIndexOf('.')))) {
      if (goog.getObjectByName(namespace)) {
        break;
      }
      goog.implicitNamespaces_[namespace] = true;
    }
  }

  goog.exportPath_(name, opt_obj);
};


/**
 * Returns CSP nonce, if set for any script tag.
 * @param {?Window=} opt_window The window context used to retrieve the nonce.
 *     Defaults to global context.
 * @return {string} CSP nonce or empty string if no nonce is present.
 */
goog.getScriptNonce = function(opt_window) {
  if (opt_window && opt_window != goog.global) {
    return goog.getScriptNonce_(opt_window.document);
  }
  if (goog.cspNonce_ === null) {
    goog.cspNonce_ = goog.getScriptNonce_(goog.global.document);
  }
  return goog.cspNonce_;
};


/**
 * According to the CSP3 spec a nonce must be a valid base64 string.
 * @see https://www.w3.org/TR/CSP3/#grammardef-base64-value
 * @private @const
 */
goog.NONCE_PATTERN_ = /^[\w+/_-]+[=]{0,2}$/;


/**
 * @private {?string}
 */
goog.cspNonce_ = null;


/**
 * Returns CSP nonce, if set for any script tag.
 * @param {!Document} doc
 * @return {string} CSP nonce or empty string if no nonce is present.
 * @private
 */
goog.getScriptNonce_ = function(doc) {
  var script = doc.querySelector && doc.querySelector('script[nonce]');
  if (script) {
    // Try to get the nonce from the IDL property first, because browsers that
    // implement additional nonce protection features (currently only Chrome) to
    // prevent nonce stealing via CSS do not expose the nonce via attributes.
    // See https://github.com/whatwg/html/issues/2369
    var nonce = script['nonce'] || script.getAttribute('nonce');
    if (nonce && goog.NONCE_PATTERN_.test(nonce)) {
      return nonce;
    }
  }
  return '';
};


/**
 * Module identifier validation regexp.
 * Note: This is a conservative check, it is very possible to be more lenient,
 *   the primary exclusion here is "/" and "\" and a leading ".", these
 *   restrictions are intended to leave the door open for using goog.require
 *   with relative file paths rather than module identifiers.
 * @private
 */
goog.VALID_MODULE_RE_ = /^[a-zA-Z_$][a-zA-Z0-9._$]*$/;


/**
 * Defines a module in Closure.
 *
 * Marks that this file must be loaded as a module and claims the namespace.
 *
 * A namespace may only be defined once in a codebase. It may be defined using
 * goog.provide() or goog.module().
 *
 * goog.module() has three requirements:
 * - goog.module may not be used in the same file as goog.provide.
 * - goog.module must be the first statement in the file.
 * - only one goog.module is allowed per file.
 *
 * When a goog.module annotated file is loaded, it is enclosed in
 * a strict function closure. This means that:
 * - any variables declared in a goog.module file are private to the file
 * (not global), though the compiler is expected to inline the module.
 * - The code must obey all the rules of "strict" JavaScript.
 * - the file will be marked as "use strict"
 *
 * NOTE: unlike goog.provide, goog.module does not declare any symbols by
 * itself. If declared symbols are desired, use
 * goog.module.declareLegacyNamespace().
 *
 *
 * See the public goog.module proposal: http://goo.gl/Va1hin
 *
 * @param {string} name Namespace provided by this file in the form
 *     "goog.package.part", is expected but not required.
 * @return {void}
 */
goog.module = function(name) {
  if (!goog.isString(name) || !name ||
      name.search(goog.VALID_MODULE_RE_) == -1) {
    throw new Error('Invalid module identifier');
  }
  if (!goog.isInGoogModuleLoader_()) {
    throw new Error(
        'Module ' + name + ' has been loaded incorrectly. Note, ' +
        'modules cannot be loaded as normal scripts. They require some kind of ' +
        'pre-processing step. You\'re likely trying to load a module via a ' +
        'script tag or as a part of a concatenated bundle without rewriting the ' +
        'module. For more info see: ' +
        'https://github.com/google/closure-library/wiki/goog.module:-an-ES6-module-like-alternative-to-goog.provide.');
  }
  if (goog.moduleLoaderState_.moduleName) {
    throw new Error('goog.module may only be called once per module.');
  }

  // Store the module name for the loader.
  goog.moduleLoaderState_.moduleName = name;
  if (!COMPILED) {
    // Ensure that the same namespace isn't provided twice.
    // A goog.module/goog.provide maps a goog.require to a specific file
    if (goog.isProvided_(name)) {
      throw new Error('Namespace "' + name + '" already declared.');
    }
    delete goog.implicitNamespaces_[name];
  }
};


/**
 * @param {string} name The module identifier.
 * @return {?} The module exports for an already loaded module or null.
 *
 * Note: This is not an alternative to goog.require, it does not
 * indicate a hard dependency, instead it is used to indicate
 * an optional dependency or to access the exports of a module
 * that has already been loaded.
 * @suppress {missingProvide}
 */
goog.module.get = function(name) {

  return goog.module.getInternal_(name);
};


/**
 * @param {string} name The module identifier.
 * @return {?} The module exports for an already loaded module or null.
 * @private
 */
goog.module.getInternal_ = function(name) {
  if (!COMPILED) {
    if (name in goog.loadedModules_) {
      return goog.loadedModules_[name].exports;
    } else if (!goog.implicitNamespaces_[name]) {
      var ns = goog.getObjectByName(name);
      return ns != null ? ns : null;
    }
  }
  return null;
};


/**
 * Types of modules the debug loader can load.
 * @enum {string}
 */
goog.ModuleType = {
  ES6: 'es6',
  GOOG: 'goog'
};


/**
 * @private {?{
 *   moduleName: (string|undefined),
 *   declareLegacyNamespace:boolean,
 *   type: ?goog.ModuleType
 * }}
 */
goog.moduleLoaderState_ = null;


/**
 * @private
 * @return {boolean} Whether a goog.module or an es6 module is currently being
 *     initialized.
 */
goog.isInModuleLoader_ = function() {
  return goog.isInGoogModuleLoader_() || goog.isInEs6ModuleLoader_();
};


/**
 * @private
 * @return {boolean} Whether a goog.module is currently being initialized.
 */
goog.isInGoogModuleLoader_ = function() {
  return !!goog.moduleLoaderState_ &&
      goog.moduleLoaderState_.type == goog.ModuleType.GOOG;
};


/**
 * @private
 * @return {boolean} Whether an es6 module is currently being initialized.
 */
goog.isInEs6ModuleLoader_ = function() {
  var inLoader = !!goog.moduleLoaderState_ &&
      goog.moduleLoaderState_.type == goog.ModuleType.ES6;

  if (inLoader) {
    return true;
  }

  var jscomp = goog.global['$jscomp'];

  if (jscomp) {
    // jscomp may not have getCurrentModulePath if this is a compiled bundle
    // that has some of the runtime, but not all of it. This can happen if
    // optimizations are turned on so the unused runtime is removed but renaming
    // and Closure pass are off (so $jscomp is still named $jscomp and the
    // goog.provide/require calls still exist).
    if (typeof jscomp.getCurrentModulePath != 'function') {
      return false;
    }

    // Bundled ES6 module.
    return !!jscomp.getCurrentModulePath();
  }

  return false;
};


/**
 * Provide the module's exports as a globally accessible object under the
 * module's declared name.  This is intended to ease migration to goog.module
 * for files that have existing usages.
 * @suppress {missingProvide}
 */
goog.module.declareLegacyNamespace = function() {
  if (!COMPILED && !goog.isInGoogModuleLoader_()) {
    throw new Error(
        'goog.module.declareLegacyNamespace must be called from ' +
        'within a goog.module');
  }
  if (!COMPILED && !goog.moduleLoaderState_.moduleName) {
    throw new Error(
        'goog.module must be called prior to ' +
        'goog.module.declareLegacyNamespace.');
  }
  goog.moduleLoaderState_.declareLegacyNamespace = true;
};


/**
 * Associates an ES6 module with a Closure module ID so that is available via
 * goog.require. The associated ID  acts like a goog.module ID - it does not
 * create any global names, it is merely available via goog.require /
 * goog.module.get / goog.forwardDeclare / goog.requireType. goog.require and
 * goog.module.get will return the entire module as if it was import *'d. This
 * allows Closure files to reference ES6 modules for the sake of migration.
 *
 * @param {string} namespace
 * @suppress {missingProvide}
 */
goog.declareModuleId = function(namespace) {
  if (!COMPILED) {
    if (!goog.isInEs6ModuleLoader_()) {
      throw new Error(
          'goog.declareModuleId may only be called from ' +
          'within an ES6 module');
    }
    if (goog.moduleLoaderState_ && goog.moduleLoaderState_.moduleName) {
      throw new Error(
          'goog.declareModuleId may only be called once per module.');
    }
    if (namespace in goog.loadedModules_) {
      throw new Error(
          'Module with namespace "' + namespace + '" already exists.');
    }
  }
  if (goog.moduleLoaderState_) {
    // Not bundled - debug loading.
    goog.moduleLoaderState_.moduleName = namespace;
  } else {
    // Bundled - not debug loading, no module loader state.
    var jscomp = goog.global['$jscomp'];
    if (!jscomp || typeof jscomp.getCurrentModulePath != 'function') {
      throw new Error(
          'Module with namespace "' + namespace +
          '" has been loaded incorrectly.');
    }
    var exports = jscomp.require(jscomp.getCurrentModulePath());
    goog.loadedModules_[namespace] = {
      exports: exports,
      type: goog.ModuleType.ES6,
      moduleId: namespace
    };
  }
};


/**
 * Marks that the current file should only be used for testing, and never for
 * live code in production.
 *
 * In the case of unit tests, the message may optionally be an exact namespace
 * for the test (e.g. 'goog.stringTest'). The linter will then ignore the extra
 * provide (if not explicitly defined in the code).
 *
 * @param {string=} opt_message Optional message to add to the error that's
 *     raised when used in production code.
 */
goog.setTestOnly = function(opt_message) {
  if (goog.DISALLOW_TEST_ONLY_CODE) {
    opt_message = opt_message || '';
    throw new Error(
        'Importing test-only code into non-debug environment' +
        (opt_message ? ': ' + opt_message : '.'));
  }
};


/**
 * Forward declares a symbol. This is an indication to the compiler that the
 * symbol may be used in the source yet is not required and may not be provided
 * in compilation.
 *
 * The most common usage of forward declaration is code that takes a type as a
 * function parameter but does not need to require it. By forward declaring
 * instead of requiring, no hard dependency is made, and (if not required
 * elsewhere) the namespace may never be required and thus, not be pulled
 * into the JavaScript binary. If it is required elsewhere, it will be type
 * checked as normal.
 *
 * Before using goog.forwardDeclare, please read the documentation at
 * https://github.com/google/closure-compiler/wiki/Bad-Type-Annotation to
 * understand the options and tradeoffs when working with forward declarations.
 *
 * @param {string} name The namespace to forward declare in the form of
 *     "goog.package.part".
 */
goog.forwardDeclare = function(name) {};


/**
 * Forward declare type information. Used to assign types to goog.global
 * referenced object that would otherwise result in unknown type references
 * and thus block property disambiguation.
 */
goog.forwardDeclare('Document');
goog.forwardDeclare('HTMLScriptElement');
goog.forwardDeclare('XMLHttpRequest');


if (!COMPILED) {
  /**
   * Check if the given name has been goog.provided. This will return false for
   * names that are available only as implicit namespaces.
   * @param {string} name name of the object to look for.
   * @return {boolean} Whether the name has been provided.
   * @private
   */
  goog.isProvided_ = function(name) {
    return (name in goog.loadedModules_) ||
        (!goog.implicitNamespaces_[name] &&
         goog.isDefAndNotNull(goog.getObjectByName(name)));
  };

  /**
   * Namespaces implicitly defined by goog.provide. For example,
   * goog.provide('goog.events.Event') implicitly declares that 'goog' and
   * 'goog.events' must be namespaces.
   *
   * @type {!Object<string, (boolean|undefined)>}
   * @private
   */
  goog.implicitNamespaces_ = {'goog.module': true};

  // NOTE: We add goog.module as an implicit namespace as goog.module is defined
  // here and because the existing module package has not been moved yet out of
  // the goog.module namespace. This satisifies both the debug loader and
  // ahead-of-time dependency management.
}


/**
 * Returns an object based on its fully qualified external name.  The object
 * is not found if null or undefined.  If you are using a compilation pass that
 * renames property names beware that using this function will not find renamed
 * properties.
 *
 * @param {string} name The fully qualified name.
 * @param {Object=} opt_obj The object within which to look; default is
 *     |goog.global|.
 * @return {?} The value (object or primitive) or, if not found, null.
 */
goog.getObjectByName = function(name, opt_obj) {
  var parts = name.split('.');
  var cur = opt_obj || goog.global;
  for (var i = 0; i < parts.length; i++) {
    cur = cur[parts[i]];
    if (!goog.isDefAndNotNull(cur)) {
      return null;
    }
  }
  return cur;
};


/**
 * Globalizes a whole namespace, such as goog or goog.lang.
 *
 * @param {!Object} obj The namespace to globalize.
 * @param {Object=} opt_global The object to add the properties to.
 * @deprecated Properties may be explicitly exported to the global scope, but
 *     this should no longer be done in bulk.
 */
goog.globalize = function(obj, opt_global) {
  var global = opt_global || goog.global;
  for (var x in obj) {
    global[x] = obj[x];
  }
};


/**
 * Adds a dependency from a file to the files it requires.
 * @param {string} relPath The path to the js file.
 * @param {!Array<string>} provides An array of strings with
 *     the names of the objects this file provides.
 * @param {!Array<string>} requires An array of strings with
 *     the names of the objects this file requires.
 * @param {boolean|!Object<string>=} opt_loadFlags Parameters indicating
 *     how the file must be loaded.  The boolean 'true' is equivalent
 *     to {'module': 'goog'} for backwards-compatibility.  Valid properties
 *     and values include {'module': 'goog'} and {'lang': 'es6'}.
 */
goog.addDependency = function(relPath, provides, requires, opt_loadFlags) {
  if (!COMPILED && goog.DEPENDENCIES_ENABLED) {
    goog.debugLoader_.addDependency(relPath, provides, requires, opt_loadFlags);
  }
};




// NOTE(nnaze): The debug DOM loader was included in base.js as an original way
// to do "debug-mode" development.  The dependency system can sometimes be
// confusing, as can the debug DOM loader's asynchronous nature.
//
// With the DOM loader, a call to goog.require() is not blocking -- the script
// will not load until some point after the current script.  If a namespace is
// needed at runtime, it needs to be defined in a previous script, or loaded via
// require() with its registered dependencies.
//
// User-defined namespaces may need their own deps file. For a reference on
// creating a deps file, see:
// Externally: https://developers.google.com/closure/library/docs/depswriter
//
// Because of legacy clients, the DOM loader can't be easily removed from
// base.js.  Work was done to make it disableable or replaceable for
// different environments (DOM-less JavaScript interpreters like Rhino or V8,
// for example). See bootstrap/ for more information.


/**
 * @define {boolean} Whether to enable the debug loader.
 *
 * If enabled, a call to goog.require() will attempt to load the namespace by
 * appending a script tag to the DOM (if the namespace has been registered).
 *
 * If disabled, goog.require() will simply assert that the namespace has been
 * provided (and depend on the fact that some outside tool correctly ordered
 * the script).
 */
goog.ENABLE_DEBUG_LOADER = goog.define('goog.ENABLE_DEBUG_LOADER', true);


/**
 * @param {string} msg
 * @private
 */
goog.logToConsole_ = function(msg) {
  if (goog.global.console) {
    goog.global.console['error'](msg);
  }
};


/**
 * Implements a system for the dynamic resolution of dependencies that works in
 * parallel with the BUILD system.
 *
 * Note that all calls to goog.require will be stripped by the compiler.
 *
 * @see goog.provide
 * @param {string} namespace Namespace (as was given in goog.provide,
 *     goog.module, or goog.declareModuleId) in the form
 *     "goog.package.part".
 * @return {?} If called within a goog.module or ES6 module file, the associated
 *     namespace or module otherwise null.
 */
goog.require = function(namespace) {
  if (!COMPILED) {
    // Might need to lazy load on old IE.
    if (goog.ENABLE_DEBUG_LOADER) {
      goog.debugLoader_.requested(namespace);
    }

    // If the object already exists we do not need to do anything.
    if (goog.isProvided_(namespace)) {
      if (goog.isInModuleLoader_()) {
        return goog.module.getInternal_(namespace);
      }
    } else if (goog.ENABLE_DEBUG_LOADER) {
      var moduleLoaderState = goog.moduleLoaderState_;
      goog.moduleLoaderState_ = null;
      try {
        goog.debugLoader_.load_(namespace);
      } finally {
        goog.moduleLoaderState_ = moduleLoaderState;
      }
    }

    return null;
  }
};


/**
 * Requires a symbol for its type information. This is an indication to the
 * compiler that the symbol may appear in type annotations, yet it is not
 * referenced at runtime.
 *
 * When called within a goog.module or ES6 module file, the return value may be
 * assigned to or destructured into a variable, but it may not be otherwise used
 * in code outside of a type annotation.
 *
 * Note that all calls to goog.requireType will be stripped by the compiler.
 *
 * @param {string} namespace Namespace (as was given in goog.provide,
 *     goog.module, or goog.declareModuleId) in the form
 *     "goog.package.part".
 * @return {?}
 */
goog.requireType = function(namespace) {
  // Return an empty object so that single-level destructuring of the return
  // value doesn't crash at runtime when using the debug loader. Multi-level
  // destructuring isn't supported.
  return {};
};


/**
 * Path for included scripts.
 * @type {string}
 */
goog.basePath = '';


/**
 * A hook for overriding the base path.
 * @type {string|undefined}
 */
goog.global.CLOSURE_BASE_PATH;


/**
 * Whether to attempt to load Closure's deps file. By default, when uncompiled,
 * deps files will attempt to be loaded.
 * @type {boolean|undefined}
 */
goog.global.CLOSURE_NO_DEPS;


/**
 * A function to import a single script. This is meant to be overridden when
 * Closure is being run in non-HTML contexts, such as web workers. It's defined
 * in the global scope so that it can be set before base.js is loaded, which
 * allows deps.js to be imported properly.
 *
 * The first parameter the script source, which is a relative URI. The second,
 * optional parameter is the script contents, in the event the script needed
 * transformation. It should return true if the script was imported, false
 * otherwise.
 * @type {(function(string, string=): boolean)|undefined}
 */
goog.global.CLOSURE_IMPORT_SCRIPT;


/**
 * Null function used for default values of callbacks, etc.
 * @return {void} Nothing.
 */
goog.nullFunction = function() {};


/**
 * When defining a class Foo with an abstract method bar(), you can do:
 * Foo.prototype.bar = goog.abstractMethod
 *
 * Now if a subclass of Foo fails to override bar(), an error will be thrown
 * when bar() is invoked.
 *
 * @type {!Function}
 * @throws {Error} when invoked to indicate the method should be overridden.
 */
goog.abstractMethod = function() {
  throw new Error('unimplemented abstract method');
};


/**
 * Adds a `getInstance` static method that always returns the same
 * instance object.
 * @param {!Function} ctor The constructor for the class to add the static
 *     method to.
 * @suppress {missingProperties} 'instance_' isn't a property on 'Function'
 *     but we don't have a better type to use here.
 */
goog.addSingletonGetter = function(ctor) {
  // instance_ is immediately set to prevent issues with sealed constructors
  // such as are encountered when a constructor is returned as the export object
  // of a goog.module in unoptimized code.
  // Delcare type to avoid conformance violations that ctor.instance_ is unknown
  /** @type {undefined|!Object} @suppress {underscore} */
  ctor.instance_ = undefined;
  ctor.getInstance = function() {
    if (ctor.instance_) {
      return ctor.instance_;
    }
    if (goog.DEBUG) {
      // NOTE: JSCompiler can't optimize away Array#push.
      goog.instantiatedSingletons_[goog.instantiatedSingletons_.length] = ctor;
    }
    // Cast to avoid conformance violations that ctor.instance_ is unknown
    return /** @type {!Object|undefined} */ (ctor.instance_) = new ctor;
  };
};


/**
 * All singleton classes that have been instantiated, for testing. Don't read
 * it directly, use the `goog.testing.singleton` module. The compiler
 * removes this variable if unused.
 * @type {!Array<!Function>}
 * @private
 */
goog.instantiatedSingletons_ = [];


/**
 * @define {boolean} Whether to load goog.modules using `eval` when using
 * the debug loader.  This provides a better debugging experience as the
 * source is unmodified and can be edited using Chrome Workspaces or similar.
 * However in some environments the use of `eval` is banned
 * so we provide an alternative.
 */
goog.LOAD_MODULE_USING_EVAL = goog.define('goog.LOAD_MODULE_USING_EVAL', true);


/**
 * @define {boolean} Whether the exports of goog.modules should be sealed when
 * possible.
 */
goog.SEAL_MODULE_EXPORTS = goog.define('goog.SEAL_MODULE_EXPORTS', goog.DEBUG);


/**
 * The registry of initialized modules:
 * The module identifier or path to module exports map.
 * @private @const {!Object<string, {exports:?,type:string,moduleId:string}>}
 */
goog.loadedModules_ = {};


/**
 * True if the debug loader enabled and used.
 * @const {boolean}
 */
goog.DEPENDENCIES_ENABLED = !COMPILED && goog.ENABLE_DEBUG_LOADER;


/**
 * @define {string} How to decide whether to transpile.  Valid values
 * are 'always', 'never', and 'detect'.  The default ('detect') is to
 * use feature detection to determine which language levels need
 * transpilation.
 */
// NOTE(sdh): we could expand this to accept a language level to bypass
// detection: e.g. goog.TRANSPILE == 'es5' would transpile ES6 files but
// would leave ES3 and ES5 files alone.
goog.TRANSPILE = goog.define('goog.TRANSPILE', 'detect');

/**
 * @define {boolean} If true assume that ES modules have already been
 * transpiled by the jscompiler (in the same way that transpile.js would
 * transpile them - to jscomp modules). Useful only for servers that wish to use
 * the debug loader and transpile server side. Thus this is only respected if
 * goog.TRANSPILE is "never".
 */
goog.ASSUME_ES_MODULES_TRANSPILED =
    goog.define('goog.ASSUME_ES_MODULES_TRANSPILED', false);


/**
 * @define {string} If a file needs to be transpiled what the output language
 * should be. By default this is the highest language level this file detects
 * the current environment supports. Generally this flag should not be set, but
 * it could be useful to override. Example: If the current environment supports
 * ES6 then by default ES7+ files will be transpiled to ES6, unless this is
 * overridden.
 *
 * Valid values include: es3, es5, es6, es7, and es8. Anything not recognized
 * is treated as es3.
 *
 * Note that setting this value does not force transpilation. Just if
 * transpilation occurs this will be the output. So this is most useful when
 * goog.TRANSPILE is set to 'always' and then forcing the language level to be
 * something lower than what the environment detects.
 */
goog.TRANSPILE_TO_LANGUAGE = goog.define('goog.TRANSPILE_TO_LANGUAGE', '');


/**
 * @define {string} Path to the transpiler.  Executing the script at this
 * path (relative to base.js) should define a function $jscomp.transpile.
 */
goog.TRANSPILER = goog.define('goog.TRANSPILER', 'transpile.js');


/**
 * @package {?boolean}
 * Visible for testing.
 */
goog.hasBadLetScoping = null;


/**
 * @return {boolean}
 * @package Visible for testing.
 */
goog.useSafari10Workaround = function() {
  if (goog.hasBadLetScoping == null) {
    var hasBadLetScoping;
    try {
      hasBadLetScoping = !eval(
          '"use strict";' +
          'let x = 1; function f() { return typeof x; };' +
          'f() == "number";');
    } catch (e) {
      // Assume that ES6 syntax isn't supported.
      hasBadLetScoping = false;
    }
    goog.hasBadLetScoping = hasBadLetScoping;
  }
  return goog.hasBadLetScoping;
};


/**
 * @param {string} moduleDef
 * @return {string}
 * @package Visible for testing.
 */
goog.workaroundSafari10EvalBug = function(moduleDef) {
  return '(function(){' + moduleDef +
      '\n' +  // Terminate any trailing single line comment.
      ';' +   // Terminate any trailing expression.
      '})();\n';
};


/**
 * @param {function(?):?|string} moduleDef The module definition.
 */
goog.loadModule = function(moduleDef) {
  // NOTE: we allow function definitions to be either in the from
  // of a string to eval (which keeps the original source intact) or
  // in a eval forbidden environment (CSP) we allow a function definition
  // which in its body must call `goog.module`, and return the exports
  // of the module.
  var previousState = goog.moduleLoaderState_;
  try {
    goog.moduleLoaderState_ = {
      moduleName: '',
      declareLegacyNamespace: false,
      type: goog.ModuleType.GOOG
    };
    var exports;
    if (goog.isFunction(moduleDef)) {
      exports = moduleDef.call(undefined, {});
    } else if (goog.isString(moduleDef)) {
      if (goog.useSafari10Workaround()) {
        moduleDef = goog.workaroundSafari10EvalBug(moduleDef);
      }

      exports = goog.loadModuleFromSource_.call(undefined, moduleDef);
    } else {
      throw new Error('Invalid module definition');
    }

    var moduleName = goog.moduleLoaderState_.moduleName;
    if (goog.isString(moduleName) && moduleName) {
      // Don't seal legacy namespaces as they may be used as a parent of
      // another namespace
      if (goog.moduleLoaderState_.declareLegacyNamespace) {
        goog.constructNamespace_(moduleName, exports);
      } else if (
          goog.SEAL_MODULE_EXPORTS && Object.seal &&
          typeof exports == 'object' && exports != null) {
        Object.seal(exports);
      }

      var data = {
        exports: exports,
        type: goog.ModuleType.GOOG,
        moduleId: goog.moduleLoaderState_.moduleName
      };
      goog.loadedModules_[moduleName] = data;
    } else {
      throw new Error('Invalid module name \"' + moduleName + '\"');
    }
  } finally {
    goog.moduleLoaderState_ = previousState;
  }
};


/**
 * @private @const
 */
goog.loadModuleFromSource_ = /** @type {function(string):?} */ (function() {
  // NOTE: we avoid declaring parameters or local variables here to avoid
  // masking globals or leaking values into the module definition.
  'use strict';
  var exports = {};
  eval(arguments[0]);
  return exports;
});


/**
 * Normalize a file path by removing redundant ".." and extraneous "." file
 * path components.
 * @param {string} path
 * @return {string}
 * @private
 */
goog.normalizePath_ = function(path) {
  var components = path.split('/');
  var i = 0;
  while (i < components.length) {
    if (components[i] == '.') {
      components.splice(i, 1);
    } else if (
        i && components[i] == '..' && components[i - 1] &&
        components[i - 1] != '..') {
      components.splice(--i, 2);
    } else {
      i++;
    }
  }
  return components.join('/');
};


/**
 * Provides a hook for loading a file when using Closure's goog.require() API
 * with goog.modules.  In particular this hook is provided to support Node.js.
 *
 * @type {(function(string):string)|undefined}
 */
goog.global.CLOSURE_LOAD_FILE_SYNC;


/**
 * Loads file by synchronous XHR. Should not be used in production environments.
 * @param {string} src Source URL.
 * @return {?string} File contents, or null if load failed.
 * @private
 */
goog.loadFileSync_ = function(src) {
  if (goog.global.CLOSURE_LOAD_FILE_SYNC) {
    return goog.global.CLOSURE_LOAD_FILE_SYNC(src);
  } else {
    try {
      /** @type {XMLHttpRequest} */
      var xhr = new goog.global['XMLHttpRequest']();
      xhr.open('get', src, false);
      xhr.send();
      // NOTE: Successful http: requests have a status of 200, but successful
      // file: requests may have a status of zero.  Any other status, or a
      // thrown exception (particularly in case of file: requests) indicates
      // some sort of error, which we treat as a missing or unavailable file.
      return xhr.status == 0 || xhr.status == 200 ? xhr.responseText : null;
    } catch (err) {
      // No need to rethrow or log, since errors should show up on their own.
      return null;
    }
  }
};


/**
 * Lazily retrieves the transpiler and applies it to the source.
 * @param {string} code JS code.
 * @param {string} path Path to the code.
 * @param {string} target Language level output.
 * @return {string} The transpiled code.
 * @private
 */
goog.transpile_ = function(code, path, target) {
  var jscomp = goog.global['$jscomp'];
  if (!jscomp) {
    goog.global['$jscomp'] = jscomp = {};
  }
  var transpile = jscomp.transpile;
  if (!transpile) {
    var transpilerPath = goog.basePath + goog.TRANSPILER;
    var transpilerCode = goog.loadFileSync_(transpilerPath);
    if (transpilerCode) {
      // This must be executed synchronously, since by the time we know we
      // need it, we're about to load and write the ES6 code synchronously,
      // so a normal script-tag load will be too slow. Wrapped in a function
      // so that code is eval'd in the global scope.
      (function() {
        eval(transpilerCode + '\n//# sourceURL=' + transpilerPath);
      }).call(goog.global);
      // Even though the transpiler is optional, if $gwtExport is found, it's
      // a sign the transpiler was loaded and the $jscomp.transpile *should*
      // be there.
      if (goog.global['$gwtExport'] && goog.global['$gwtExport']['$jscomp'] &&
          !goog.global['$gwtExport']['$jscomp']['transpile']) {
        throw new Error(
            'The transpiler did not properly export the "transpile" ' +
            'method. $gwtExport: ' + JSON.stringify(goog.global['$gwtExport']));
      }
      // transpile.js only exports a single $jscomp function, transpile. We
      // grab just that and add it to the existing definition of $jscomp which
      // contains the polyfills.
      goog.global['$jscomp'].transpile =
          goog.global['$gwtExport']['$jscomp']['transpile'];
      jscomp = goog.global['$jscomp'];
      transpile = jscomp.transpile;
    }
  }
  if (!transpile) {
    // The transpiler is an optional component.  If it's not available then
    // replace it with a pass-through function that simply logs.
    var suffix = ' requires transpilation but no transpiler was found.';
    transpile = jscomp.transpile = function(code, path) {
      // TODO(sdh): figure out some way to get this error to show up
      // in test results, noting that the failure may occur in many
      // different ways, including in loadModule() before the test
      // runner even comes up.
      goog.logToConsole_(path + suffix);
      return code;
    };
  }
  // Note: any transpilation errors/warnings will be logged to the console.
  return transpile(code, path, target);
};

//==============================================================================
// Language Enhancements
//==============================================================================


/**
 * This is a "fixed" version of the typeof operator.  It differs from the typeof
 * operator in such a way that null returns 'null' and arrays return 'array'.
 * @param {?} value The value to get the type of.
 * @return {string} The name of the type.
 */
goog.typeOf = function(value) {
  var s = typeof value;
  if (s == 'object') {
    if (value) {
      // Check these first, so we can avoid calling Object.prototype.toString if
      // possible.
      //
      // IE improperly marshals typeof across execution contexts, but a
      // cross-context object will still return false for "instanceof Object".
      if (value instanceof Array) {
        return 'array';
      } else if (value instanceof Object) {
        return s;
      }

      // HACK: In order to use an Object prototype method on the arbitrary
      //   value, the compiler requires the value be cast to type Object,
      //   even though the ECMA spec explicitly allows it.
      var className = Object.prototype.toString.call(
          /** @type {!Object} */ (value));
      // In Firefox 3.6, attempting to access iframe window objects' length
      // property throws an NS_ERROR_FAILURE, so we need to special-case it
      // here.
      if (className == '[object Window]') {
        return 'object';
      }

      // We cannot always use constructor == Array or instanceof Array because
      // different frames have different Array objects. In IE6, if the iframe
      // where the array was created is destroyed, the array loses its
      // prototype. Then dereferencing val.splice here throws an exception, so
      // we can't use goog.isFunction. Calling typeof directly returns 'unknown'
      // so that will work. In this case, this function will return false and
      // most array functions will still work because the array is still
      // array-like (supports length and []) even though it has lost its
      // prototype.
      // Mark Miller noticed that Object.prototype.toString
      // allows access to the unforgeable [[Class]] property.
      //  15.2.4.2 Object.prototype.toString ( )
      //  When the toString method is called, the following steps are taken:
      //      1. Get the [[Class]] property of this object.
      //      2. Compute a string value by concatenating the three strings
      //         "[object ", Result(1), and "]".
      //      3. Return Result(2).
      // and this behavior survives the destruction of the execution context.
      if ((className == '[object Array]' ||
           // In IE all non value types are wrapped as objects across window
           // boundaries (not iframe though) so we have to do object detection
           // for this edge case.
           typeof value.length == 'number' &&
               typeof value.splice != 'undefined' &&
               typeof value.propertyIsEnumerable != 'undefined' &&
               !value.propertyIsEnumerable('splice')

               )) {
        return 'array';
      }
      // HACK: There is still an array case that fails.
      //     function ArrayImpostor() {}
      //     ArrayImpostor.prototype = [];
      //     var impostor = new ArrayImpostor;
      // this can be fixed by getting rid of the fast path
      // (value instanceof Array) and solely relying on
      // (value && Object.prototype.toString.vall(value) === '[object Array]')
      // but that would require many more function calls and is not warranted
      // unless closure code is receiving objects from untrusted sources.

      // IE in cross-window calls does not correctly marshal the function type
      // (it appears just as an object) so we cannot use just typeof val ==
      // 'function'. However, if the object has a call property, it is a
      // function.
      if ((className == '[object Function]' ||
           typeof value.call != 'undefined' &&
               typeof value.propertyIsEnumerable != 'undefined' &&
               !value.propertyIsEnumerable('call'))) {
        return 'function';
      }

    } else {
      return 'null';
    }

  } else if (s == 'function' && typeof value.call == 'undefined') {
    // In Safari typeof nodeList returns 'function', and on Firefox typeof
    // behaves similarly for HTML{Applet,Embed,Object}, Elements and RegExps. We
    // would like to return object for those and we can detect an invali