1.1 goog.inherits
goog.inherits = function(childCtor, parentCtor) { function tempCtor() { }; // 声明临时函数 tempCtor tempCtor.prototype = parentCtor.prototype; // 临时函数的原型指向父构造函数的原型 childCtor.superClass_ = parentCtor.prototype; //给子对象构造函数添加superClass_属性,指向父对象构造函数的原型对象 childCtor.prototype = new tempCtor(); // 子对象的原型指向 tempCtor的实例 childCtor.prototype.constructor = childCtor; // 子对象原型对象的构建函数指向自己 //子构造函数绑定base方法,调用父构造函数原型对象方法 childCtor.base = function(me, methodName, var_args) { var args = new Array(arguments.length - 2); for (var i = 2; i < arguments.length; i++) { args[i - 2] = arguments[i]; //获取参数 } //执行父对象的方法 return parentCtor.prototype[methodName].apply(me, args); }; };
通过goog.inherits()完成了:
干净的继承父构造函数的原型对象.
增强子构造函数,可以通过childCtor的base方法和所需方法名调用父构造函数原型对象的方法。
为子构造函数新加了一个属性,指向父构造函数的原型对象。
参考链接: https://www.cnblogs.com/vivihoo03/p/5651020.html
1.2 goog.base
base: function (me, opt_methodName, var_args) { var caller = arguments.callee.caller; // 这个属性保存着调用当前函数的函数的引用 if (caller.superClass_) { // Copying using loop to avoid deop due to passing arguments object to // function. This is faster in many JS engines as of late 2014. var ctorArgs = new Array(arguments.length - 1); for (var i = 1; i < arguments.length; i++) { ctorArgs[i - 1] = arguments[i]; } // This is a constructor. Call the superclass constructor. return caller.superClass_.constructor.apply(me, ctorArgs); } // Copying using loop to avoid deop due to passing arguments object to // function. This is faster in many JS engines as of late 2014. var args = new Array(arguments.length - 2); for (var i = 2; i < arguments.length; i++) { args[i - 2] = arguments[i]; } var foundCaller = false; for (var ctor = me.constructor; ctor; ctor = ctor.superClass_ && ctor.superClass_.constructor) { if (ctor.prototype[opt_methodName] === caller) { foundCaller = true; } else if (foundCaller) { return ctor.prototype[opt_methodName].apply(me, args); } } // If we did not find the caller in the prototype chain, then one of two // things happened: // 1) The caller is an instance method. // 2) This method was not called by the right caller. if (me[opt_methodName] === caller) { return me.constructor.prototype[opt_methodName].apply(me, args); } else { console.log( 'goog.base called from a method of one name ' + 'to a method of a different name'); } }