/*
* @ call和apply方法
* @ 当一个object没有某个方法，但是其他的有，我们可以借助call或apply用其它对象的方法来操作。
* @ (有方法的)对象.call("环境的上下文本对象",参数)
* @ 通过call和apply，我们可以实现对象继承。示例
*//*function product(test){alert(test);}function log(){}product.call(log,2);*//*function product(test){alert(test);}function log(){product.call(this,2);}log();*/function Product(name, price){this.name = name;this.price = price;if(price < 0){throw RangeError('Cannot create product ' + this.name + ' with a negative price');}}// call方法function Food(name,price){Product.call(this,name,price);this.category = "food";}// 等同于function Food(name,price){this.name = name;this.price = price;if(price < 0){throw RangeError('Cannot create product ' + this.name + ' with a negative price');}this.category = "food";}// 以DOM为例子/*function changeStyle(attr, value){this.style[attr] = value;}var box = document.getElementById('box');window.changeStyle.call(box, "height", "200px");window.changeStyle.apply(box, ['height', '200px']);*//*// 实现继承var Parent = function(){this.name = "yc",this.age = "1"}var child = {};Parent.call(child); // 实现继承*//*log("%c红色的字, %c绿色的字, %c大象", "color:red", "color:green", "line-height:100px;padding:50px;background:url(http://fanjs.net/res/img/favicon.ico");*/function say(name){console.log(this + "," + name);}say.call2 = function( thisObj, arg1 ) {thisObj = new Object( thisObj );thisObj.say = this;return thisObj.say(arg1);};say.call2("hola","Mike");/*
* object.prototype.call
* @ 当一个object没有某个方法，但是其他的有，我们可以借助call或apply用其它对象的方法来操作。
* @ 语法: fun.call(thisArg[, arg1[, arg2[, ...]]])
* @ param: thisArg {object} //当前引用对象
* @ 不传参数,传null,undefined, this指向window对象
* @ 传递另一个函数的函数名fun2, this指向函数fun2的引用
* @ 传递一个对象,函数中的this指向这个对象
* @ 值为原始值(数字,字符串,布尔值), this会指向该原始值的自动包装对象,如String,Number,Boolean
* @ param: arg1, arg2, ... {object} // arguments参数
*/// call函数中的this指向
function a(){console.log(this);
}
function b(){}var objthis = {name: "Alan"}; //定义对象
a.call(); // window
a.call(null); // window
a.call(undefined); // window
a.call(1); // Number {[[PrimitiveValue]]: 1}
a.call(""); // String {length: 0, [[PrimitiveValue]]: ""}
a.call(true); // Boolean {[[PrimitiveValue]]: true}
a.call(b); // function b(){}
a.call(objthis); // Object {name: "Alan"}// 使用call对象的构造函数链
function Product(name, price){this.name = name;this.price = price;if(price < 0){throw RangeError("Cannot create product " + this.name + " with negative price");}
}function Food(name,price){Product.call(this,name,price);this.category = "food"
}
var cheese = new Food("feta",5);// 使用call调用匿名函数
var animals = [{species: "Lion",name: "king"},{species: "Whale",name: "Fail"}
]for(var i = 0; i < animals.length; i++){(function(i){this.print = function(){console.log("#" + i + " " + this.species + ": " + this.name);}this.print();}).call(animals[i],i);// 等同于/*(function(){this.print = function(){console.log("#" + i + " " + animals[i].species + ": " + animals[i].name);}this.print();})();*/
}// 使用call调用函数的上下文this
function greet(){var reply = [this.person, "Is An Awesome", this.role].join(" ");console.log(reply);
}var obj = {person: "Douglas Crockford", role: "Javascript Developer"
};greet.call(obj);
