nixfilter/utils.js

Simplify the development of (UNIX) "Filters"

'use strict';
var extend, first_valid_value, is_valid_value, mixin_factory, mixin_own;

// Creates and returns mixin function (<object>, <mixin_objects...>) -> that mixins all properties for which <key_filter_function>(<key>, <mixin_object>, <object>) returns true into <object>
mixin_factory = function(key_filter_function) {
  return function(object, ...mixin_objects) {
    var i, key, len, mixin_object;
    for (i = 0, len = mixin_objects.length; i < len; i++) {
      mixin_object = mixin_objects[i];
      if (mixin_object) {
        for (key in mixin_object) {
          if (key_filter_function(key, mixin_object, object)) {
            object[key] = mixin_object[key];
          }
        }
      }
    }
    return object;
  };
};

// (<object>, <mixin_objects...>) -> Mixin all OWN properties of <mixin_objects...> into <object>
mixin_own = mixin_factory(function(key, mixin_object) {
  return mixin_object.hasOwnProperty(key);
});

extend = function(parent, properties, static_properties) {
  var child;
  child = ((properties != null ? properties.hasOwnProperty('constructor') : void 0) ? properties.constructor : (function() {
    return parent.apply(this, arguments);
  }));
  child.prototype = Object.create(parent.prototype);
  mixin_own(child.prototype, properties);
  child.prototype.constructor = child;
  return mixin_own(child, parent, static_properties);
};

// Returns true if the passed argument <value> is neither null nor undefined
is_valid_value = function(value) {
  return (value !== void 0) && (value !== null);
};

// Returns the first value in <values...> that is neither null nor undefined
first_valid_value = function(...values) {
  var i, len, value;
  for (i = 0, len = values.length; i < len; i++) {
    value = values[i];
    if (is_valid_value(value)) {
      return value;
    }
  }
};

// What this module exports
module.exports = {
  extend: extend,
  first_valid_value: first_valid_value,
  mixin_own: mixin_own
};

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