JavaScript函数中this指向问题详解

function fn(){
	console.log(this);
	// 此时 this 指向 window
}
fn();
// 相当于 window.fn()

var obj = {
	fn:function(){
		console.log(this);
	}
}
obj.fn();
// 此时 this 指向 obj

setTimeout(function(){
	console.log(this);	
},0)
// 此时定时器处理函数里面的this 指向 window

div.onclick = function(){
	console.log(this);
}
//当你点击 div 的时候，this指向 div

(function () {
  console.log(this)
})()
// 此时 this 指向 window

var num = 666;

function fn() {
  console.log('num = ', this.num);
}

fn.call();  // num = 666

var name = 'Rose';
var obj = {name:'Jack'};
function fn(){
	console.log(this.name);
}
fn();	// Rose
fn.call();	// Rose
fn.call(obj);  // jack

var name = 'Rack';
var obj = {name:'Jack'};
function fn(a,b){
	console.log(this,a,b);
}
fn(1,2);	// window 1 2
fn.call(obj,1,2);	// obj 1 2
fn(1,3);	// window 1 3

var obj = {name:'jack'};
function fn(a,b){
	console.log(this,a,b);
}
fn(1,2);	// window 1 2
fn.apply(obj,[1,2]);	// obj 1 2

var arr1 = [1,2];
var arr2 = [3,4];
arr1.push(arr2);
console.log(arr1);	//	[1,2,[3,4]]	

var arr1 = [1,2];
var arr2 = [3,4];

var arr3 = arr1.concat(arr2);
console.log(arr1);	// [1,2]
console.log(arr3);	// [1,2,3,4]

var arr1 = [1,2];
var arr2 = [3,4];

arr1.push.apply(arr1,arr2);
console.log(arr1);	// [1,2,3,4]

/* 找出数组中最大/小的数字 */
var numbers = [5, 6, 2, 3, 7];

var max = Math.max(numbers)
var min = Math.min(numbers)
console.log(min,max);	// NaN NaN

var max = Math.max.apply(null, numbers); 
/* 基本等同于 Math.max(numbers[0], ...) 或 Math.max(5, 6, ..) */
var min = Math.min.apply(null, numbers);
console.log(min,max);	// 2 7

var obj = {name:'jack'};
function fn(a,b){
	console.log(this,a,b);
}
fn(1,2);	// window 1 2
fn.bind(obj,1,2);	// 未调用不执行
fn.bind(obj,1,3)()	// obj 1 3
var newFn = fn.bind(obj,3,4);
newFn();	// obj 1 4
newFn(5,6);	// obj 3 4