首先讯屈，給出個人的理解：with就是為了封裝某個對象县习，減少某個對象的調(diào)用
比如：定義一個對象
var a={},a.name='張三';a.sex='女';
一般的調(diào)用方式
console.log(a.name);
console.log(a.sex);
使用with之后的調(diào)用
with(a){
console.log(name);
console.log(sex);
}
以下給出示例代碼
<div id='div1'>test</div>
<script>
var a = {};
a.aa = 1;
a.bb = 2;
a.cc = 3; with(a) {
console.log(aa);
console.log(bb);
console.log(cc);
} var b = function() { this.a = 111; this.b = 222;
}
b.prototype.test = function(param) { this.a = param;
console.log(this.a)
}; with(new b()) {
test('just for test');
} var div1 = document.getElementById('div1'); with(div1.style) {
width = '200px';
height = '300px';
background = 'red';
color = 'white';
} </script>
轉(zhuǎn)載出處：https://www.cnblogs.com/benchan2015/p/5057314.html
