About the understanding of this in js function
//关于this的问题 第一个情况：
function Foo() {
this.name=10;
this.age=100;
console.log(this) //{name:10, age:100}
}
// var p=new Foo(); new 一个对象，this指的就是即将new出来的对象
// Foo() 调用情况下，this指window 输出{window}//关于this的问题 第二种情况：var obj={
x:5,
fn:function () {
console.log(this); //obj{x:10,fn:function}
console.log(this.x); //5
}
};
obj();
//函数作为对象的一个属性被调用时，this指该对象，即obj//关于this的问题 第三种情况：var obj= {
x: 10,
fn: function () {
console.log(this); //Window
console.log(this.x); //undefined
}
};
var fun=obj.fn;
fun()
//这里fn函数被赋值到另一个变量中，没有作为obj一个属性被调用，则this指window//关于this的问题 第四种情况：
var obj={ x:20}
var fn =function () {
console.log(this); //Object {x:20}
console.log(this.x) //20
}
fn.call(obj);
//当一个函数被call或apply调用时，this则取传入的对象的值或者：var x=20;var fn = function(){ console.log(this) //window console.log(this.x) //20};fn(); //调用fn函数时，this指的是window//关于this的问题 第五种情况：var obj={
x:10,
fn:function(){
function f(){
console.log(this); //window
console.log(this.x) //undefined
}
f()
}
};
obj.fn()
// 函数f虽然是在函数内部定义的，但仍然是普通函数，this指window.The above is the detailed content of About the understanding of this in js function. For more information, please follow other related articles on the PHP Chinese website!
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