1.this use
this
js中的关键字
js内部已经定义好了,可以不声明 直接使用
this的指向问题
1. 在函数外部使用
this指向的是window
2. 在函数内部使用
有名函数
直接调用函数 this指的还是window
通过事件调用，事件是谁触发的 this指的就是谁
匿名函数
通过事件调用，事件是谁触发的 this指的就是谁
<body>
<div id="box">box</div>
<script>
alert(this); //[object Window]
//------------------------------------------
function fn(){
alert( this );
}
fn(); // 直接调用 ,函数内的this 指的还是 [object Window]
document.onclick = fn; //[object HTMLDocument]
var box = document.getElementById("box");
box.onclick = fn; //[object HTMLDivElement]
//------------------------------------------
// 匿名函数 由事件调用,事件由谁触发 this指向谁
document.onclick = function(){
alert(this);
};
var box = document.getElementById("box");
box.onclick = function(){
alert(this);
}
</script>
</body>2. Analog radio button
Single-box simulation results of FIG.
Method a: cleansing, before setting the color to set the color values of all empty. Then click the box to set the color.
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style>
div{
width:100px;
height:100px;
border: 1px solid #000;
display: inline-block;
}
</style>
</head>
<body>
<div></div>
<div></div>
<div></div>
<script>
var divs = document.getElementsByTagName("div");
for (var i = 0; i < divs.length; i++) {
// alert( "for执行中,此次i是" + i);
// alert( "此次为 第 "+ i +" 个div 添加点击事件处理函数" )
divs[i].onclick = function(){
// alert(i);
// 把 所有的 div 颜色 清除
for (var i = 0; i < divs.length; i++) {
divs[i].style.backgroundColor = "";
}
// 为点击的这个div添加颜色
this.style.backgroundColor = "cornflowerblue";
}
}
</script>
</body>
</html>Method Two: Click on what, what to remove. Click on the current record.
<body>
<div></div>
<div></div>
<div></div>
<script>
var divs=document.getElementsByTagName("div");
var now=0;
for( var i=0; i<divs.length;i++){
divs[i].index=i;//建立索引，记录每一个节点值。
divs[i].onclick=function () {
divs[now].style.background="";
this.style.background="coral";
now=this.index;
}
}
</script>
</body>3. Tab
Method a: cleansing, before setting the color to set the color values of all empty. Then click the box to set the color.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
div{
width: 100px;
height: 100px;
background: red;
font:20px/2 "宋体";
color:#fff;
display: none;
margin-top: 20px;
}
button{
width: 100px;
line-height: 50px;
font-size:18px;
background: none;
}
.show{
display: block;
}
.active{
background: cornflowerblue;
}
</style>
</head>
<body>
<button class="active">选项卡一</button>
<button>选项卡二</button>
<button>选项卡三</button>
<div class="show">内容一</div>
<div>内容二</div>
<div>内容三</div>
<script>
var btns=document.getElementsByTagName("button");
var divs=document.getElementsByTagName("div");
for(var i=0;i<divs.length;i++){
btns[i].index=i;
btns[i].onclick=function () {
for(var i=0;i<divs.length;i++) {
btns[i].className="";
divs[i].className="";
}
this.className="active";
divs[this.index].className="show";
}
}
</script>
</body>
</html>Method Two: Click on what, what to remove. Click on the current record.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
div{
width: 100px;
height: 100px;
background: red;
font:20px/2 "宋体";
color:#fff;
display: none;
margin-top: 20px;
}
button{
width: 100px;
line-height: 50px;
font-size:18px;
background: none;
}
.show{
display: block;
}
.active{
background: cornflowerblue;
}
</style>
</head>
<body>
<button class="active">选项卡一</button>
<button>选项卡二</button>
<button>选项卡三</button>
<div class="show">内容一</div>
<div>内容二</div>
<div>内容三</div>
<script>
var btns=document.getElementsByTagName("button");
var divs=document.getElementsByTagName("div");
var now=0;
for(var i=0;i<divs.length;i++){
btns[i].index=i;
btns[i].onclick=function () {
btns[now].className="";
divs[now].className="";
this.className="active";
divs[this.index].className="show";
now=this.index;
}
}
</script>
</body>
</html>4. Analog box
Simulation and code box to see the effect! ! ! !
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
div{
width: 100px;
height: 100px;
border:1px solid black;
float: left;
margin-right: 10px;
}
.active{
background: cornflowerblue;
}
</style>
</head>
<body>
<div></div>
<div></div>
<div></div>
<script>
var divs=document.getElementsByTagName("div");
console.log(divs);
var L=divs.length;
for(var i=0;i<L;i++){
// true表示没被点击
// false表示被点击了
divs[i].onoff=true;
divs[i].onclick=function () {
if(this.onoff){//如果没被点击，则添加背景颜色
this.className="active";
}else{//如果点击了，则清空背景颜色
this.className="";
}
this.onoff=!this.onoff;//只要点击了，就将此div的自定义属性值取反。
}
}
</script>
</body>
</html>