34 lines
1.0 KiB
JavaScript
34 lines
1.0 KiB
JavaScript
var isFunction = require('./type/is-function');
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var mix = require('./mix');
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var extend = function extend(subclass, superclass, overrides, staticOverrides) {
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// 如果只提供父类构造函数，则自动生成子类构造函数
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if (!isFunction(superclass)) {
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overrides = superclass;
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superclass = subclass;
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subclass = function subclass() {};
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}
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var create = Object.create ? function (proto, c) {
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return Object.create(proto, {
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constructor: {
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value: c
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}
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});
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} : function (proto, c) {
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function Tmp() {}
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Tmp.prototype = proto;
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var o = new Tmp();
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o.constructor = c;
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return o;
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};
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var superObj = create(superclass.prototype, subclass); // new superclass(),//实例化父类作为子类的prototype
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subclass.prototype = mix(superObj, subclass.prototype); // 指定子类的prototype
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subclass.superclass = create(superclass.prototype, superclass);
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mix(superObj, overrides);
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mix(subclass, staticOverrides);
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return subclass;
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};
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module.exports = extend; |