---
# System prepended metadata

title: "\U0001F3C5 Day 02 - 型別與宣告"
tags: [2025 Node.js 後端工程師培訓營]

---

# 🏅 Day 02 - 型別與宣告

### 題目

以下兩題請合併為一份 CodePen 繳交，並透過「註解」進行回答。


問題一
---
以下變數 a, b, c, d, e, f 它們的值、型別各自為何? (請先想想看，不要用 console.log 檢查)

```javascript=
let a = "10" + "10";
let b = "10" * "10";
let c = 10 + "10";
let d = 10 * "10";
let e = 10 - "2";
let f = "10" - "2";
```
範例回答格式：
```javascript=
// 問題一：
// a = 值, 型別
// b = 值, 型別
```

問題二
---
請問以下題項哪些是有問題的，並說明為什麼。



``` js=
// 1
let myName = "jay";

// 2
var _state = true;

// 3
let true = true;

// 4
const 520Pretty = 520;

// 5
const appleNum = 10;
appleNum = 2;

// 6
var ming ='小明';
var ming = '小民';

// 7
const ming = '小明'; 
const ming = '小民'; 

// 8
let ming = '小明';
let ming = '小民'; 

// 9
let ming = '小明';
ming = '小民';

// 10
let $open = "芝麻開門';
```

範例回答格式：
```javascript=
// 問題二
// (2)，因為 blablabla 
// (3)，因為 balabababa 
```


## 回報流程

將答案寫在 CodePen 並複製 CodePen 連結貼至底下回報就算完成了喔! 
解答位置請參考下圖（需打開程式碼的部分觀看）

![](https://i.imgur.com/vftL5i0.png)

<!-- 解答：  

問題一：
a = "1010"，string
b = 100，number
c = "1010"，string
d = 100，number
e = 8，number
f = 8，number

問題二：
(3)，關鍵字不可以用來作為變數名稱
(4)，變數名稱的開頭不可以使用數字
(5)，const 不可以重新被指派值
(7)，因為 const 不可重複宣告，會呈現 Uncaught SyntaxError
(8)，因為 let 不可重複宣告，會呈現 Uncaught SyntaxError
(10)，"芝麻開門' 的引號必須成對

-->




回報區
---
| #   | Discord | CodePen / 答案 |
|-----|---------|---------------|
| 1   | 偉青(.weiching_721)  | [Codepen](https://codepen.io/lovegull/pen/YPKYEKp?editors=0010)               |
| 2   | 馬德(qwerasd718)  | [Codepen](https://codepen.io/maywang/pen/PwYEOQa?editors=0010)               |
| 3   | ss585801.  | [Codepen](https://codepen.io/ss585801/pen/qEWppEV?editors=0012)               |
| 4   | HarryKuo  | [Codepen](https://codepen.io/harry_kuo/pen/ZYzvvBB?editors=0011)               |
| 5   | Tau  | [Codepen](https://codepen.io/Tau-Hsu/pen/ogvppxq?editors=1112)               |
| 6   | yutzu  | [Codepen](https://codepen.io/dtafsrmf-the-lessful/pen/MYgrrye?editors=0010)               |
| 7   | Ali    | [Codepen](https://codepen.io/Alicia1117/pen/YPKYYvB)               |
| 8   | 柴郡貓(bian_yang_mofa) |   [Codepen](https://codepen.io/cssf998811/pen/QwLaQLp?editors=0010) | 
| 9   | Wayne_957 | [Codepen](https://codepen.io/Wayne957/pen/EaYooBR)
| 10  | hsiang4100 |   [Codepen](https://codepen.io/vvnrbgxl-the-typescripter/pen/KwPZQBR?editors=0011) | 
| 11  | adengg |   [Codepen](https://codepen.io/Osases/pen/KwPZQJB?editors=0010) | 
| 12  | ZoeKang | [CodePen](https://codepen.io/byehywmx-the-animator/pen/mybpXzO?editors=0011) |
| 13  | CC(tofuuu_cat) | [CodePen](https://codepen.io/CC-cat/pen/ogvpqjL?editors=0010) |
| 14  | poyi | [CodePen](https://codepen.io/poyi-the-flexboxer/pen/ogvpEGv?editors=0012) |
| 14  | Benson | [CodePen](https://codepen.io/DevilButler/pen/KwPZoRL) |
| 15  | 不好說 | [Codepen](https://codepen.io/zarr12steven/pen/wBwpmKm?editors=0012) |
| 16  | mu mu | [Codepen](https://codepen.io/ishuki916/pen/yyBpKmN) |
| 17  | Arsian Kuo | [Codepen](https://codepen.io/Arsian-Kuo/pen/mybpLxg) |
| 18  | ally_tsao           | [Codepen](https://codepen.io/ggnhmrxv-the-scripter/pen/PwYEazN?editors=0010)|
| 19  | Tammy |   [Codepen](https://codepen.io/Tammy_Tsai/pen/LEPerJY) | 
| 20  | Nora |   [Codepen](https://codepen.io/ehguhcmy-the-reactor/pen/gbYojaG) |
| 21  | JC |   [Codepen](https://codepen.io/lifetimingwhisper/pen/bNbajVM) |
| 22  | Sui |   [Codepen](https://codepen.io/suihsilan/pen/KwPZBxj?editors=0010) |
|23|Lee | [Codepen](https://codepen.io/leemo-tseng/pen/raBpKoP)
| 24  | Jayhsu |   [Codepen](https://codepen.io/Jay-Hsu-the-bold/pen/GgKyXzV?editors=1111) |
| 25  | ya_meow | [Codepen](https://codepen.io/gkfxzvcb-the-bashful/pen/emOyLEv?editors=0010)|
| 26  | helena | [Codepen](https://codepen.io/helena27/pen/pvzazbr)|
| 27  | JerryOOO | [Codepen](https://codepen.io/fatiangel/pen/QwLaQOO?editors=0011)|
| 28  | jameschen5522 | [Codepen](https://codepen.io/frswsqve-the-selector/pen/JoPpXYm?editors=0011)|
| 29  | 0111mina | [Codepen](https://codepen.io/0111mina/pen/KwPQMNG?editors=0012)|
| 30  | penny_5754 | [Codepen](https://codepen.io/bmxbpggh-the-flexboxer/pen/qEWqNxN)|
| 31  | xuanchen0610 | [Codepen](https://codepen.io/YiXuan-Chen-the-vuer/pen/ByBYLQb)|
| 32  | JanllyGuo | [Codepen](https://codepen.io/kedugaw/pen/mybXrdK)|
| 33  | shiang |[Codepen](https://codepen.io/shiang29/pen/raBJaMW?editors=0010)|
| 34| daffytseng |[Codepen](https://codepen.io/Daffy-Tseng/pen/azoqwem) |
| 35| chun0075 |[Codepen](https://codepen.io/Lin-Angela/pen/JoPpRwv?editors=0011) |
| 36| Li Wei-Nin |[Codepen](https://codepen.io/leewayne/pen/dPbdzvd) |
|37|----這條線以下都麻糬----|[Codepen](https://codepen.io/tsfaydhk-the-selector/pen/qEWxMvY?editors=0012)|
|38|地呱|[Codepen](https://codepen.io/pen/?editors=1111)|
|39|weins_jo3jo3|[Codepen](https://codepen.io/Shao-the-selector/pen/jENYvQM?editors=0011)|
|40|will092317|[Codepen](https://codepen.io/xuazoblx-the-flexboxer/pen/xbKYPxv)|
|41|pja._.|[Codepen](https://codepen.io/PJA0103/pen/RNbMgGR?editors=0010)|
|42|Rylee|[Codepen](https://codepen.io/ryleezheng/pen/azoGwag)|
|43|641|[Codepen](https://codepen.io/Liu641/pen/emOrRQx?editors=0011)|
|44| Cami  | [Codepen](https://codepen.io/irisLife/pen/pvzVWZR) | 
|45|hsin yu|   [Codepen](https://codepen.io/tina2793778/pen/gbYKoPW?editors=0010)| 
|46|wuyuli_21403|   [Codepen](https://codepen.io/Job-Wilhelm/pen/OPLZqgR)| 
|47|gagalala|   [Codepen](https://codepen.io/nohungry/pen/azoxmEm?editors=1111)| 
| 48 | Cami | [Codepen](https://codepen.io/irisLife/pen/EaxgroP) |

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