# 4.7 操控 class 屬性

## .classList.add()

讓某元素加上指定的 class。

## .classList.remove()

讓某元素移除指定的 class。

## .classList.contains()

判斷某元素是否存在某個 class。

## .classList.toggle()

某元素若存在某個 class，就移除；反之，就加上。

## 範例

{% embed url="<https://codepen.io/carlos411/pen/QWNdEez>" %}

## .style 的寫法

```javascript
var the_block = document.getElementById("the_block");
the_block.style.opacity = 0.2;
the_block.style.backgroundColor = "blue";
```

範例：

{% embed url="<https://codepen.io/carlos411/pen/RwaQmmr>" %}


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