JavaScript
不推荐内联
第一段JavaScript：
<!DOCTYPE html>
<html>
<body>
<h2>我的第一段 JavaScript</h2>
<button type="button"
onclick="document.getElementById('demo').innerHTML = Date()">
点击这里来显示日期和时间
</button>
<p id="demo"></p>
</body>
</html>
内部的 JavaScript ：
<!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">
<link rel="stylesheet" href="./css/style.css">
<title>JavaScript Crash Course</title>
</head>
<body>
<div class="header">
<h1>JavaScript Crash Course</h1>
</div>
<div class="container">
</div>
</body>
<script>
alert(Math.PI);
</script>
</html>
alert：浏览器广播
alert("Hello" + "World");
外部的JavaScript
新建js文件，在body后面：
<script src="main.js"></script>
console.log在控制台输出
console.log("hello".length);
console.log("hello".charAt(0)); //第0个
console.log("hello, world".replace("hello","goodbye")); //替换
console.log("hello, world".toUpperCase()); //大写
新建变量var 、 let ，输出：
（var在哪都是全局变量，let是局部变量）
var name = "DasAuto"; console.log(name); let a = 1; console.log(a);a = 1+1; console.log(a);
定义常量：const （值不变）
const Pi = 3.14; console.log(Pi);
x = "3"+4+5 == x = "3"+"4"+"5"
var x; x = "3"+4+5; console.log(x);
输出345；（有字符串之后都以字符串形式处理）。
var x; x = 4+5+"3"; console.log(x);
输出93；
var name = "Simon";
var age =12
var allowed = (age>=18)? "yes":"no";
console.log(allowed);
switch(name){
case 'Simon':
console.log("Simon");
break;
case 'John':
console.log("John");
break;
default:
console.log("Stranger");
}
数组
var obj = new Object();
var obj2 = {};
obj = {
name: "Simon",
age: '20',
email:"[email protected]",
contact:{
phone:"123456",
Telegram:"@Simon"
}
};
console.log(obj.contact)
var a = new Array();
var b = [];
a[0] = "dog";
a[1] = "cat";
a[5] = "tiger";
console.log(a)
b = ["dog","cat","tiger"];
console.log(b);
for(let i=0;i<b.length;i++){
console.log(b[i]);
}
for (let i in a){
console.log(a[i]);
}
//for in 遍历非空数组
添加数组
b = ["dog","cat","tiger"];
b.push("sheep"); //从末尾添加
b.reverse(); //翻转
b.shift(0); //删除第一个
b.unshift("lion"); //从开头添加
console.log(b);
数组各种属性用法推荐去看：
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array函数：
let a = 1;
function add(x){
a += x;
}
add(4);
console.log(a);
function add(){
let sum = 0;
for( let i = 0, j = arguments.length;i<j;i++){
sum+=arguments[i];
}
return sum;
}
let sum = add(1,2,3,4,5);
console.log(sum);
结果15
闭包：
多继承
function makeAdder(a){
return function(b){
return a+b;
};
}
var x = makeAdder(5);
var sum = x(6);
console.log(sum);
得到11。
总代码：
html：
<!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">
<link rel="stylesheet" href="./css/style.css">
<title>JavaScript Crash Course</title>
</head>
<body>
<div class="header">
<h1>JavaScript Crash Course</h1>
</div>
<div class="container">
</div>
</body>
<script src="main.js"></script>
</html>
css：
body {
text-align: center;
font-family: Arial, Helvetica, sans-serif;
font-size: 18px;
}
.header{
color: pink;
background-color: #f4f4f4;
border: #ccc 3px solid;
padding: 20px;
}
.container{
width: 700px;
margin: 30px auto;
}
js：
function makeAdder(a){
return function(b){
return a+b;
};
}
var x = makeAdder(5);
var sum = x(6);
console.log(sum);
右键检查：查看控制台的输出
23.1.29
标签：Simon,console,log,JavaScript,笔记,速成,let,var From： https://www.cnblogs.com/Burn-Hep/p/17073061.html