# Node.js/javascript
- [Hello world](#Hello-world)
- [變數](#變數)
- [let 與 var 差別](#let與var差別)
- [const](#const)
- [判斷式](#判斷式)
-[等號的區別](#等號的區別)
- [迴圈](#迴圈)
- [物件](#物件)
---
## Hello world
```js
console.log("Hello world")
```
## 變數
### let與var差別
```js
var a = 0;
let b = 0;
console.log(`a: ${a}`);
console.log(`b: ${a}`);
for(let i=0;i<10;i++){
var a = i+1;
let b = i+1;
}
console.log(`a: ${a}`);
console.log(`b: ${b}`);
```
---
### const
```js
const a = 0;
a = 10;
console.log(a);
//錯誤不能執行
```
---
const 好廢?
---
不他很有用!之後會提到
---
# 判斷式
---
## 等號的區別
= 、 == 、 ===這三個有什麼不同
* = 這個我們上面用過了是右邊的值賦予到左邊的變數裡
```js
a = 10;
```
---
* ==判斷兩邊值是否相等是回傳true不是回傳false
```js
console.log(1 == 1) // true
console.log(1 == 0) // false
```
---
* ===判斷兩邊值**以及型態**是否相等是回傳true不是回傳false
```js
console.log(1 === "1") // false
console.log(1 == "1") // true
console.log(1 === 1) // true
```
---
## 物件
用{}包裝起來，並且索引與值成對中間用冒號分隔的就教物件
```js
{索引:"值"}
{a:2}
```
---
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