Ext3.1—继承

原谅我的吐槽

从公司待了这么久，一直为公司无私奉献着。用的差点上个是世纪的ExtJs3.1！一直有转站前端的想法。于是决定在原地起航，从ExtJs源码分析着手。通过自己对源码的阅读和分析，实际应用，和extjs源码分析开发宝典这本书一起。把心得和收获记录于此。

本次先把我之前对继承的研究贴出来。
经过对Ext.js的阅读 把继承相关的代码分离出来，并添加注释。

var Ext = {};Ext.isIE = (function() {    var ua ='opera', //navigator.userAgent.toLowerCase(),        check = function(r) {            return r.test(ua);        },        isOpera = check(/opera/);    return !isOpera && check(/msie/);})();Ext.isObject = function(v) {    return !!v && Object.prototype.toString.call(v) === '[object Object]'; //如果是函数 [object Function]};Ext.apply = function(o, c, defaults) {    // no "this" reference for friendly out of scope calls    if (defaults) {        Ext.apply(o, defaults);    }    if (o && c && typeof c == 'object') {        for (var p in c) {            o[p] = c[p];        }    }    return o;};Ext.override = function(origclass, overrides) {    if (overrides) {        var p = origclass.prototype;        Ext.apply(p, overrides);        if (Ext.isIE && overrides.hasOwnProperty('toString')) {            p.toString = overrides.toString;        }    }};Ext.extend = function() {    // inline overrides    var io = function(o) {        for (var m in o) {            this[m] = o[m];        }    };    //书中扩展；~并没有好用的/*  var superclass = function(sp){        var s = function(){return arguments.callee.superclass;};        s.superclass=sp;        return s;    }*/    var oc = Object.prototype.constructor;    return function(sb, sp, overrides) {        //sp如果是对象，实际只传入两个参数，Sb是自动生成的        //sp如果不是对象，就当是子类函数        if (Ext.isObject(sp)) {            overrides = sp;            sp = sb;            sb = overrides.constructor != oc ? overrides.constructor : function() {                sp.apply(this, arguments);            };        }        var F = function() {},            sbp, spp = sp.prototype;        F.prototype = spp;        sbp = sb.prototype = new F();        sbp.constructor = sb;        sb.superclass = spp;        if (spp.constructor == oc) {            spp.constructor = sp;        }        sb.override = function(o) {            Ext.override(sb, o);        };        /*sbp.superclass = sbp.supr = superclass(spp)*/        sbp.superclass = sbp.supr = (function() {            return spp;        });//加一层括号暂时看不出意图 知乎解释：分组运算符，与不加效果完全一样        sbp.override = io;        Ext.override(sb, overrides);        sb.extend = function(o) {            return Ext.extend(sb, o);        };        return sb;    };}();

测试代码

var A = function(){    console.log('A执行')    this.A=1;}var B = Ext.extend(A, {    constructor:function(B){        console.log('B执行')        console.log(this.superclass())        //A.apply(this, arguments);        this.superclass().constructor(B);        this.B=B;    },    B: 3});var C = Ext.extend(B,{    constructor:function(C){        console.log('C执行')        console.log(this.superclass())        this.superclass().constructor(7)        this.C=C;    },    C: 3});var b =new B(5);var c =new C(8);console.log(b,c,b);console.log(b.supr);