class-utils/index.js

'use strict';

var util = require('util');
var define = require('define-property');
var isObj = require('isobject');

/**
 * Expose class utils: `cu`
 */

var cu = exports = module.exports;

cu.isObject = function isObject(val) {
  return isObj(val) || typeof val === 'function';
};

/**
 * Returns true if an array has any of the given elements, or an
 * object has any of the give keys.
 *
 * ```js
 * cu.has(['a', 'b', 'c'], 'c');
 * //=> true
 *
 * cu.has(['a', 'b', 'c'], ['c', 'z']);
 * //=> true
 *
 * cu.has({a: 'b', c: 'd'}, ['c', 'z']);
 * //=> true
 * ```
 * @param {Object} `obj`
 * @param {String|Array} `val`
 * @return {Boolean}
 * @api public
 */

cu.has = function has(obj, val) {
  val = cu.arrayify(val);
  var len = val.length;

  if (cu.isObject(obj)) {
    for (var key in obj) {
      if (val.indexOf(key) > -1) {
        return true;
      }
    }

    var keys = cu.nativeKeys(obj);
    return cu.has(keys, val);
  }

  if (Array.isArray(obj)) {
    var arr = obj;
    while (len--) {
      if (arr.indexOf(val[len]) > -1) {
        return true;
      }
    }
    return false;
  }

  throw new TypeError('expected an array or object.');
};

/**
 * Returns true if an array or object has all of the given values.
 *
 * ```js
 * cu.hasAll(['a', 'b', 'c'], 'c');
 * //=> true
 *
 * cu.hasAll(['a', 'b', 'c'], ['c', 'z']);
 * //=> false
 *
 * cu.hasAll({a: 'b', c: 'd'}, ['c', 'z']);
 * //=> false
 * ```
 * @param {Object|Array} `val`
 * @param {String|Array} `values`
 * @return {Boolean}
 * @api public
 */

cu.hasAll = function hasAll(val, values) {
  values = cu.arrayify(values);
  var len = values.length;
  while (len--) {
    if (!cu.has(val, values[len])) {
      return false;
    }
  }
  return true;
};

/**
 * Cast the given value to an array.
 *
 * ```js
 * cu.arrayify('foo');
 * //=> ['foo']
 *
 * cu.arrayify(['foo']);
 * //=> ['foo']
 * ```
 *
 * @param {String|Array} `val`
 * @return {Array}
 * @api public
 */

cu.arrayify = function arrayify(val) {
  return val ? (Array.isArray(val) ? val : [val]) : []
};

/**
 * Noop
 */

cu.noop = function noop() {
  return;
};

/**
 * Returns the first argument passed to the function.
 */

cu.identity = function identity(val) {
  return val;
};

/**
 * Returns true if a value has a `contructor`
 *
 * ```js
 * cu.hasConstructor({});
 * //=> true
 *
 * cu.hasConstructor(Object.create(null));
 * //=> false
 * ```
 * @param  {Object} `value`
 * @return {Boolean}
 * @api public
 */

cu.hasConstructor = function hasConstructor(val) {
  return cu.isObject(val) && typeof val.constructor !== 'undefined';
};

/**
 * Get the native `ownPropertyNames` from the constructor of the
 * given `object`. An empty array is returned if the object does
 * not have a constructor.
 *
 * ```js
 * cu.nativeKeys({a: 'b', b: 'c', c: 'd'})
 * //=> ['a', 'b', 'c']
 *
 * cu.nativeKeys(function(){})
 * //=> ['length', 'caller']
 * ```
 *
 * @param  {Object} `obj` Object that has a `constructor`.
 * @return {Array} Array of keys.
 * @api public
 */

cu.nativeKeys = function nativeKeys(val) {
  if (!cu.hasConstructor(val)) return [];
  return Object.getOwnPropertyNames(val);
};

/**
 * Returns property descriptor `key` if it's an "own" property
 * of the given object.
 *
 * ```js
 * function App() {}
 * Object.defineProperty(App.prototype, 'count', {
 *   get: function() {
 *     return Object.keys(this).length;
 *   }
 * });
 * cu.getDescriptor(App.prototype, 'count');
 * // returns:
 * // {
 * //   get: [Function],
 * //   set: undefined,
 * //   enumerable: false,
 * //   configurable: false
 * // }
 * ```
 *
 * @param {Object} `obj`
 * @param {String} `key`
 * @return {Object} Returns descriptor `key`
 * @api public
 */

cu.getDescriptor = function getDescriptor(obj, key) {
  if (!cu.isObject(obj)) {
    throw new TypeError('expected an object.');
  }
  if (typeof key !== 'string') {
    throw new TypeError('expected key to be a string.');
  }
  return Object.getOwnPropertyDescriptor(obj, key);
};

/**
 * Copy a descriptor from one object to another.
 *
 * ```js
 * function App() {}
 * Object.defineProperty(App.prototype, 'count', {
 *   get: function() {
 *     return Object.keys(this).length;
 *   }
 * });
 * var obj = {};
 * cu.copyDescriptor(obj, App.prototype, 'count');
 * ```
 * @param {Object} `receiver`
 * @param {Object} `provider`
 * @param {String} `name`
 * @return {Object}
 * @api public
 */

cu.copyDescriptor = function copyDescriptor(receiver, provider, name) {
  if (!cu.isObject(receiver)) {
    throw new TypeError('expected receiving object to be an object.');
  }
  if (!cu.isObject(provider)) {
    throw new TypeError('expected providing object to be an object.');
  }
  if (typeof name !== 'string') {
    throw new TypeError('expected name to be a string.');
  }
  var val = cu.getDescriptor(provider, name);
  if (val) define(receiver, name, val);
};

/**
 * Copy static properties, prototype properties, and descriptors
 * from one object to another.
 *
 * @param {Object} `receiver`
 * @param {Object} `provider`
 * @param {String|Array} `omit` One or more properties to omit
 * @return {Object}
 * @api public
 */

cu.copy = function copy(receiver, provider, omit) {
  if (!cu.isObject(receiver)) {
    throw new TypeError('expected receiving object to be an object.');
  }
  if (!cu.isObject(provider)) {
    throw new TypeError('expected providing object to be an object.');
  }
  var props = Object.getOwnPropertyNames(provider);
  var keys = Object.keys(provider);
  var len = props.length, key;
  omit = cu.arrayify(omit);

  while (len--) {
    key = props[len];

    if (cu.has(keys, key)) {
      define(receiver, key, provider[key]);
    } else if (!(key in receiver) && !cu.has(omit, key)) {
      cu.copyDescriptor(receiver, provider, key);
    }
  }
};

/**
 * Inherit the static properties, prototype properties, and descriptors
 * from of an object.
 *
 * @param {Object} `receiver`
 * @param {Object} `provider`
 * @param {String|Array} `omit` One or more properties to omit
 * @return {Object}
 * @api public
 */

cu.inherit = function inherit(receiver, provider, omit) {
  if (!cu.isObject(receiver)) {
    throw new TypeError('expected receiving object to be an object.');
  }
  if (!cu.isObject(provider)) {
    throw new TypeError('expected providing object to be an object.');
  }

  var keys = [];
  for (var key in provider) {
    keys.push(key);
    define(receiver, key, provider[key]);
  }

  keys = keys.concat(cu.arrayify(omit));

  var a = provider.prototype || provider;
  var b = receiver.prototype || receiver;
  cu.copy(b, a, keys);
};

/**
 * Returns a function for extending the static properties,
 * prototype properties, and descriptors from the `Parent`
 * constructor onto `Child` constructors.
 *
 * ```js
 * var extend = cu.extend(Parent);
 * Parent.extend(Child);
 *
 * // optional methods
 * Parent.extend(Child, {
 *   foo: function() {},
 *   bar: function() {}
 * });
 * ```
 * @param {Function} `Parent` Parent ctor
 *   @param {Function} `Child` Child ctor
 *   @param {Object} `proto` Optionally pass additional prototype properties to inherit.
 *   @return {Object}
 * @api public
 */

cu.extend = function extend(Parent) {
  if (typeof Parent !== 'function') {
    throw new TypeError('expected Parent to be a function.');
  }

  return function (Ctor, proto) {
    if (typeof Ctor !== 'function') {
      throw new TypeError('expected Ctor to be a function.');
    }

    util.inherits(Ctor, Parent);

    for (var key in Parent) {
      Ctor[key] = Parent[key];
    }

    if (typeof proto === 'object') {
      var obj = Object.create(proto);

      for (var k in obj) {
        Ctor.prototype[k] = obj[k];
      }
    }
    Ctor.extend = cu.extend(Ctor);
  };
};