69 lines
1.1 KiB
Markdown
69 lines
1.1 KiB
Markdown
# JavaScript基本语法
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## 变量
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声明变量
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```javascript :no-line-numbers
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var a = 1;
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```
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JavaScript有如下基本的变量类型`Number`, `String`, `Boolean`, `Undefined`, `Null`
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```javascript :no-line-numbers
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var a=1; //Number
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var b="hello"; //String`
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var c=true; //Boolean
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var d; //Undefined`
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var e=null; //Null
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```
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JavaScript 是一种动态类型语言，也就是说，变量的类型没有限制，变量可以随时更改类型。
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```javascript :no-line-numbers
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var a=1;
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a="hello";
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```
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## 流程控制
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### 条件(if...else 结构)
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```javascript :no-line-numbers
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if (m === 0)
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{
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// ...
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}
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else if (m === 1) {
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// ...
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}
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else if (m === 2) {
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// ...
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}
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else { // ... }
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```
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### switch 结构
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```javascript :no-line-numbers
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switch (fruit) {
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case "banana":
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{
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//...
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}
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break;
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case "apple":
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break;
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default:
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}
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```
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### 循环
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while循环
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```javascript :no-line-numbers
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while(condition) {
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//do something
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}
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do {
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//do something
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}while(condition)
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```
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for循环
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```javascript :no-line-numbers
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for (var i = 0; i < 3; i++) {
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console.log(i); // 0 1 2
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}
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```
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和c++一样，`continue`和`break`在循环体中起到同样作用
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