sugar/common/var/classChecks.js

A Javascript utility library for working with native objects.

'use strict';

var NATIVE_TYPES = require('./NATIVE_TYPES'),
    forEach = require('../internal/forEach'),
    isClass = require('../internal/isClass'),
    spaceSplit = require('../internal/spaceSplit'),
    isPlainObject = require('../internal/isPlainObject');

var isSerializable,
    isBoolean, isNumber, isString,
    isDate, isRegExp, isFunction,
    isArray, isSet, isMap, isError;

function buildClassChecks() {

  var knownTypes = {};

  function addCoreTypes() {

    var names = spaceSplit(NATIVE_TYPES);

    isBoolean = buildPrimitiveClassCheck(names[0]);
    isNumber  = buildPrimitiveClassCheck(names[1]);
    isString  = buildPrimitiveClassCheck(names[2]);

    isDate   = buildClassCheck(names[3]);
    isRegExp = buildClassCheck(names[4]);

    // Wanted to enhance performance here by using simply "typeof"
    // but Firefox has two major issues that make this impossible,
    // one fixed, the other not, so perform a full class check here.
    //
    // 1. Regexes can be typeof "function" in FF < 3
    //    https://bugzilla.mozilla.org/show_bug.cgi?id=61911 (fixed)
    //
    // 2. HTMLEmbedElement and HTMLObjectElement are be typeof "function"
    //    https://bugzilla.mozilla.org/show_bug.cgi?id=268945 (won't fix)
    isFunction = buildClassCheck(names[5]);

    // istanbul ignore next
    isArray = Array.isArray || buildClassCheck(names[6]);
    isError = buildClassCheck(names[7]);

    isSet = buildClassCheck(names[8], typeof Set !== 'undefined' && Set);
    isMap = buildClassCheck(names[9], typeof Map !== 'undefined' && Map);

    // Add core types as known so that they can be checked by value below,
    // notably excluding Functions and adding Arguments and Error.
    addKnownType('Arguments');
    addKnownType(names[0]);
    addKnownType(names[1]);
    addKnownType(names[2]);
    addKnownType(names[3]);
    addKnownType(names[4]);
    addKnownType(names[6]);

  }

  function addArrayTypes() {
    var types = 'Int8 Uint8 Uint8Clamped Int16 Uint16 Int32 Uint32 Float32 Float64';
    forEach(spaceSplit(types), function(str) {
      addKnownType(str + 'Array');
    });
  }

  function addKnownType(className) {
    var str = '[object '+ className +']';
    knownTypes[str] = true;
  }

  function isKnownType(className) {
    return knownTypes[className];
  }

  function buildClassCheck(className, globalObject) {
    // istanbul ignore if
    if (globalObject && isClass(new globalObject, 'Object')) {
      return getConstructorClassCheck(globalObject);
    } else {
      return getToStringClassCheck(className);
    }
  }

  // Map and Set may be [object Object] in certain IE environments.
  // In this case we need to perform a check using the constructor
  // instead of Object.prototype.toString.
  // istanbul ignore next
  function getConstructorClassCheck(obj) {
    var ctorStr = String(obj);
    return function(obj) {
      return String(obj.constructor) === ctorStr;
    };
  }

  function getToStringClassCheck(className) {
    return function(obj, str) {
      // perf: Returning up front on instanceof appears to be slower.
      return isClass(obj, className, str);
    };
  }

  function buildPrimitiveClassCheck(className) {
    var type = className.toLowerCase();
    return function(obj) {
      var t = typeof obj;
      return t === type || t === 'object' && isClass(obj, className);
    };
  }

  addCoreTypes();
  addArrayTypes();

  isSerializable = function(obj, className) {
    // Only known objects can be serialized. This notably excludes functions,
    // host objects, Symbols (which are matched by reference), and instances
    // of classes. The latter can arguably be matched by value, but
    // distinguishing between these and host objects -- which should never be
    // compared by value -- is very tricky so not dealing with it here.
    return isKnownType(className) || isPlainObject(obj, className);
  };

}

buildClassChecks();

module.exports = {
  isSerializable: isSerializable,
  isBoolean: isBoolean,
  isNumber: isNumber,
  isString: isString,
  isDate: isDate,
  isRegExp: isRegExp,
  isFunction: isFunction,
  isArray: isArray,
  isSet: isSet,
  isMap: isMap,
  isError: isError
};