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