1. let keyword
1. role: * Similar to var, it is used to declare a variable 2. characteristics: * Effective within block scope * No duplicate declaration * No preprocessing, no variable escalation 3. applications: * Loop traversal plus listening * Replacing var with let is the trend
<script type="text/javascript">
{
var a=10;
let b=20; //Effective within block scope
console.log(b)// 20
}
console.log(a);//10
console.log(b);// b is not defined; variables defined with let keywords in block scope are not visible globally
</script><script type="text/javascript">
let age = 12;
let age = 13;//No duplicate declaration
</script> console.log(age);// age is not defined error reporting
let age = 12;
console.log(sex);//undefined
var sex="male"Application: (Here) http://es6.ruanyifeng.com/ The website explains the application very well.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>01_let Keyword</title>
</head>
<body>
<button>Test 1</button>
<br>
<button>Test 2</button>
<br>
<button>Test 3</button>
<br>
<script type="text/javascript">
console.log(age);
let btns = document.getElementsByTagName('button');
for(let i = 0;i<btns.length;i++){
btns[i].onclick = function () {
alert(i);// 0 1 2
}
}
</script>
</body>2. const keyword
1. role: * Define a constant 2. characteristics: * Can not be modified * Other features are the same as let 3. applications: * Save unchanged data
const sex = 'male';
console.log(sex);
sex = 'female';//Direct Save Can't Be Modified
console.log(sex);3. Deconstruction and Assignment of Arrays and Objects
1. Understand:
* Extracting data from objects or arrays, And assign variables(Multiple)
2. Object deconstruction assignment
let {n, a} = {n:'tom', a:12}
3. Deconstruction assignment of arrays
let [a,b] = [1, 'Li Bu fan'];
4. purpose
* Assignment of multiple parameters4. Template string
1. Template String: Simplified String Splicing
* Template strings must be included with `
* The changed part is defined with ${xxx}<script type="text/javascript">
let obj = {
name : 'anverson',
age : 41
};
console.log('My name is:' + obj.name + ', My age is:' + obj.age);
console.log(`My name is:${obj.name}, My age is: ${obj.age}`);
</script>
Learn a website of es6: http://es6.ruanyifeng.com/