@antv/util/esm/extend.js

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