---
# System prepended metadata

title: "\U0001F3C5 DAY25 每日任務：forEach"
tags: [JS 直播班  - 2021 秋季班]

---

# 🏅 DAY25 每日任務：forEach
###### tags: `JS 直播班  - 2021 秋季班`


forEach 簡介
---

forEach() 是屬於 **「陣列」** 的方法，會將陣列內的每個元素一一傳入，並執行給定的函式一次。 forEach() 內的函式常見會帶有三個參數，以下為用法示例:
```js=
let data = ["a", "b", "c"];

// 參數 item 代表陣列中目前正在被處理的那個元素
// 參數 index 代表陣列中目前正在被處理的那個元素的索引值
// 參數 array 代表被處理的陣列本身，在此為 data
data.forEach(function(item, index, array){
    console.log(item, index, array);
})
```
執行結果:
![](https://i.imgur.com/NuRNgjX.png)



### 這邊需要特別提醒，在 forEach() 函式內用 return 是無效的。除非程式碼有誤，否則並沒有中止 forEach() 的辦法

```js=
let data = ["a", "b", "c"];
// 
data.forEach(function(item, index, array){
    console.log(item, index, array);
    // 程式碼會忽略這個 return
    return
})
```

問題
---
請根據以下要求撰寫程式碼:
> 1. 如果 NumberAll 陣列內的值大於或等於 30，則用 push() 方法將其加入 NumberAbove30 陣列中。
> 2. 如果 NumberAll 陣列內的值小於 30，則用 push() 方法將其加入 NumberUnder30 陣列中。

```js=
let NumberAll = [25, 30, 15, 50, 17, 40];
let NumberAbove30 = [];
let NumberUnder30 = [];

NumberAll.forEach(function(/* 填入參數 */){
    if(/* 填入判斷式 */){
        /* 程式碼撰寫處 */
    }else{
        /* 程式碼撰寫處 */
    }
});
console.log(NumberAbove30);
console.log(NumberUnder30);
```

回報流程
---
將答案寫在 CodePen 並複製 CodePen 連結貼至 thread 中回報就算完成了喔! 解答請參考下圖（需打開程式碼的部分觀看）

![](https://i.imgur.com/6UoJVtD.png)

<!-- 解答
let NumberAll = [25, 30, 15, 50, 17, 40];
let NumberAbove30 = [];
let NumberUnder30 = [];

NumberAll.forEach(function(item){
    if(item >= 30){
        NumberAbove30.push(item);
    }else{
    	NumberUnder30.push(item);
    }
});
console.log(NumberAbove30);
console.log(NumberUnder30);
-->

| Slack  |                        CodePen                        |
|:------:|:----------------------------------------------------:|
| 蔡明達 | https://codepen.io/bmzpfyxe/pen/NWgKQZB?editors=0111 |
|CloThEs | https://codepen.io/bogwdnxx-the-sans/pen/zYdJqeK|
|Karen Huang| https://codepen.io/Coding_Snorlax/pen/KKvxzbP?editors=0011 |
|Aaron Tu|https://codepen.io/aarontu/pen/porOyqo|
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|Iris Huang|https://codepen.io/ythuang/pen/abyaNrJ|
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|洋蔥|https://codepen.io/oikdkmxq-the-looper/pen/PoKdNMX?editors=0011|
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|有廖先生(Rain)|https://codepen.io/billpop741/pen/VwzGaoX |
|POPEYE | https://codepen.io/popeye_ux/pen/MWvqejj |
|jojoy|https://codepen.io/jojoy/pen/LYjJZbd?editors=0011|
| Sam | https://codepen.io/sam-hsu/pen/GRvXqWe |
|艾瑞克|https://codepen.io/ericla/pen/NWvLrjP?editors=0010|
| 劉維倫 | https://codepen.io/lun0223/pen/YzxOWQR?editors=1012 |
| Jun Ting Lin | https://codepen.io/jake1155/pen/dyzqXzq |
|Yof| https://codepen.io/yangyof/pen/RwZYRgv?editors=1011 |
| Elaine Liu | https://codepen.io/elaine7598/pen/WNEgxEQ?editors=0010 |
Tim Lin|https://codepen.io/TimmyLin/pen/KKvxMYm
| Cheng Pei-hsuan | https://codepen.io/PaCheng/pen/zYdGKpO                             |
| --------------- | ------------------------------------------------------------------ |
| Gill            | https://codepen.io/Gill-Chin/pen/NWvLrJr?editors=0011              |
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| Kelvin Hsu      | https://codepen.io/kelvin001/pen/wvqEWZG?editors=1111              |
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| Pei Ying        | https://codepen.io/Pei-Ying/pen/JjyaRKz?editors=1111               |
| Sylvia-H        | https://codepen.io/Cosmosheart/pen/dyzqpvb?editors=0011            |
| AKI             | https://codepen.io/akichen27/pen/rNzZMyZ                           |
| 群嘉            | https://codepen.io/efzdamnp-the-lessful/pen/mdMGrmV?editors=1111   |
| Yunei           | https://codepen.io/Yunei/pen/NWvLRav                               |
| 大衛            | https://codepen.io/exnsrpjc/pen/VwzBygm?editors=0011               |
| Andy Huang      | https://codepen.io/HsuHuaHuang/pen/wvqEoNN                         |
| Peggy Tsai      | https://codepen.io/pei-chi-tsai/pen/GRvXrJw?editors=0011           |
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| 蔣秉彣          | https://codepen.io/the-pierre/pen/YzxOZay?editors=1010             |
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| Genos           | https://codepen.io/pb220416/pen/ExveXZv                            |
| ZY Hsu          | https://codepen.io/zihyin/pen/Exvevap?editors=0011                 |
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| Lai             | https://codepen.io/co_lai/pen/Badqbjq?editors=0011                 |
| 鄭安志          | https://codepen.io/lwmtsgek/pen/eYEPXBp?editors=0011               |
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| 陳sam           | https://codepen.io/euldpliv/pen/yLoRrvz                            |
| 雪莉            | https://codepen.io/utshang216/pen/VwzEOpa                          |
| Joey            | https://codepen.io/Joey-Chen/pen/wvqYbYj                           |
| YuriT           | https://codepen.io/wenfisht/pen/wvqYZGa                            |
| Yashien Lin     | https://codepen.io/YashienLin/pen/QWMVqmo?editors=0010             |
| kailun          | https://codepen.io/Kailun/pen/vYJQEbY                              |
| lingxuan        | https://codepen.io/penglingxuan/pen/KKvrzqe?editors=0010           |
| Calon           | https://codepen.io/Calon0118/pen/ZEJmWpq                           |
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| Alvin           | https://codepen.io/Alvin20201116/pen/PoKxBdx?editors=1011          |
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| 乃萱            | https://codepen.io/nainaikuo/pen/abyPXPr?editors=1011              |
| LTL             | https://codepen.io/ltlin93/pen/RwZEmqa                             |
| Chia Chi        | https://codepen.io/ClaraChen/pen/wvqNGRd?editors=1111              |
| Gui             | https://codepen.io/guitimliu/pen/gOxqReX                           |
| 吐司            | https://codepen.io/malolulu/pen/oNemKaq                            |
| Ching           | https://codepen.io/Jaimedede/pen/qBXvwom?editors=1010              |
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| Zooey Cheng     | https://codepen.io/noraneko0430/pen/gOxVGyd?editors=0011           |
| Hamaji          | https://codepen.io/hamajibashi/pen/PoJYmva                         |
| Aya             | https://codepen.io/NoNameNote/pen/NWaWMjx                          |
| YOYOO           | https://codepen.io/lumedkle/pen/ExwaLww?editors=1111               |
| Jeff            | https://codepen.io/jeff-cheng/pen/GRMpeON                          |
| ShinyChen       | https://codepen.io/shinychen/pen/bGoMwGX                           |
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