let变量声明以及声明特性
- 1 let变量声明
- 2 let声明特性
- 3 let经典案例实践
1 let变量声明
<script>let a;let b,c,d;let e = 100;let f = 521, g = 'iloveyou', h = [];</script>
2 let声明特性
- 1> 变量不能重复声明
- 2> 块级作用域、全局作用域、函数作用域、eval作用域
- 3> 不存在变量提升
- 4> 不影响作用域链
<script>{let school = '北大';function fn() {console.log(school);}fn();}</script>
3 let经典案例实践
<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>let经典案例实践</title><style>.item {width: 100px;height: 50px;border: solid 1px rgb(42, 156, 156);float: left;margin-right: 10px;}</style>
</head>
<body><div class="container"><h2 class="page-header">点击切换颜色</h2><div class="item"></div><div class="item"></div><div class="item"></div></div><script>let items = document.getElementsByClassName('item');for(let i = 0; i < items.length; i++) {items[i].onclick = function () {this.style.background = 'pink';items[i].style.background = 'pink'; }}</script>
</body>