/*!
|
* static-extend <https://github.com/jonschlinkert/static-extend>
|
*
|
* Copyright (c) 2016, Jon Schlinkert.
|
* Licensed under the MIT License.
|
*/
|
|
'use strict';
|
|
var copy = require('object-copy');
|
var define = require('define-property');
|
var util = require('util');
|
|
/**
|
* Returns a function for extending the static properties,
|
* prototype properties, and descriptors from the `Parent`
|
* constructor onto `Child` constructors.
|
*
|
* ```js
|
* var extend = require('static-extend');
|
* Parent.extend = extend(Parent);
|
*
|
* // optionally pass a custom merge function as the second arg
|
* Parent.extend = extend(Parent, function(Child) {
|
* Child.prototype.mixin = function(key, val) {
|
* Child.prototype[key] = val;
|
* };
|
* });
|
*
|
* // extend "child" constructors
|
* Parent.extend(Child);
|
*
|
* // optionally define prototype methods as the second arg
|
* Parent.extend(Child, {
|
* foo: function() {},
|
* bar: function() {}
|
* });
|
* ```
|
* @param {Function} `Parent` Parent ctor
|
* @param {Function} `extendFn` Optional extend function for handling any necessary custom merging. Useful when updating methods that require a specific prototype.
|
* @param {Function} `Child` Child ctor
|
* @param {Object} `proto` Optionally pass additional prototype properties to inherit.
|
* @return {Object}
|
* @api public
|
*/
|
|
function extend(Parent, extendFn) {
|
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);
|
copy(Ctor, Parent);
|
|
// proto can be null or a plain object
|
if (typeof proto === 'object') {
|
var obj = Object.create(proto);
|
|
for (var k in obj) {
|
Ctor.prototype[k] = obj[k];
|
}
|
}
|
|
// keep a reference to the parent prototype
|
define(Ctor.prototype, '_parent_', {
|
configurable: true,
|
set: function() {},
|
get: function() {
|
return Parent.prototype;
|
}
|
});
|
|
if (typeof extendFn === 'function') {
|
extendFn(Ctor, Parent);
|
}
|
|
Ctor.extend = extend(Ctor, extendFn);
|
};
|
};
|
|
/**
|
* Expose `extend`
|
*/
|
|
module.exports = extend;
|
