---
tags: JS 直播班 - 2023 秋季班
---
# 🏅 Day 25 - forEach
[`forEach()`](https://developer.mozilla.org/zh-TW/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach) 是屬於 **「陣列」** 的方法，會將陣列內的每個元素一一傳入，並依序執行函式。 `forEach()` 內的函式常見會帶有三個參數，以下為用法示例：
```javascript=
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:
**這邊需要特別提醒，在 `forEach()` 函式內用 return 無法停止函式進行下一個 item。除非程式碼有誤，否則並沒有中止 `forEach()` 的辦法**
```javascript=
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。
```javascript=
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）
<!-- 解答：
let numberAll = [25, 30, 15, 50, 17, 40];
let numberAbove30 = [];
let numberUnder30 = [];
//forEach
numberAll.forEach(function(item) {
if (item >= 30) {
numberAbove30.push(item);
} else {
numberUnder30.push(item);
}
});
console.log(numberAbove30);
console.log(numberUnder30);
-->
回報區
---
| Discord | CodePen / 答案 |
|:---------------:|:----------------------------------------------------------------------------:|
|詹姆士|[CodePen](https://codepen.io/z111048/pen/MWLmojj)|
|⭐️小正|[CodePen](https://codepen.io/colorgolden/pen/bGzWRBb?editors=1111)|
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|Ching|[CodePen](https://codepen.io/tzuchingg/pen/WNPjOjv?editors=0011)|
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|Moreene|[CodePen](https://codepen.io/Moreene/pen/ZEwKyMJ)|
|yuling|[Codepen](https://codepen.io/igzdflpu/pen/MWLmoPo?editors=1011)|
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| 荷菓かのり | [Codepen](https://codepen.io/oogxwkvw-the-builder/pen/PoVmaqJ?editors=1112) |
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|Eden|[Codepen](https://codepen.io/iseden/pen/bGzWXXa)|
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