Node.js中的this关键字

最新推荐文章于 2024-06-23 17:51:44 发布

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最新推荐文章于 2024-06-23 17:51:44 发布

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本文通过一个简单的Node.js示例程序详细解释了this关键字在不同上下文中所指向的对象。包括构造函数、全局对象及bind、call方法的影响。

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Node.js中，this这个关键字指代哪个对象，有时容易搞混。写个简单的程序测试看看。

function TestA() {
    this.v1 = "Monday";
    var v2 = "Tuesday";
    v3 = "Wednesday";

    this.func1 = function() {
        console.log("this is " + this);
        console.log("v1 is " + this.v1);
    };
};

var obj1 = new TestA();
console.log("obj is ", obj1);
console.log("v1 is " + obj1.v1);
console.log("v2 is " + obj1.v2);
console.log("v3 is " + obj1.v3);
console.log("v3 is " + v3);
obj1.func1();

var obj2 = obj1.func1;
obj2();

var obj3 = obj2.bind(obj1);
obj3();

obj2.call(obj1);

输出结果是：

obj is  { v1: 'Monday', func1: [Function] }
v1 is Monday
v2 is undefined
v3 is undefined
v3 is Wednesday
this is [object Object]
v1 is Monday
this is [object global]
v1 is undefined
this is [object Object]
v1 is Monday
this is [object Object]
v1 is Monday