How to delete css in js

In front-end development, we often need to dynamically add, modify or delete DOM elements and CSS styles. DOM and CSS are both indispensable parts of front-end development, and JavaScript, as a scripting language, can operate on DOM and CSS.

This article will focus on how to use JavaScript to delete CSS, including the following aspects:

1. How to delete CSS
2. JavaScript operation CSS
3. Implementation example of deleting CSS
4. Notes

1. How to delete CSS

Before introducing how to delete CSS in JS, let’s first take a look at how to delete CSS in CSS , how to delete a style.

There are two ways to delete styles in CSS:

1. display:none;
2. null or empty string.

display:none; is a commonly used method to hide elements, but it is not a real deletion operation. It just changes the way the element is displayed. The element is still in the DOM. exist.

Setting the CSS style to null or empty string is a real deletion operation. However, if there are multiple CSS styles, we need to set them to null or empty string respectively to delete the styles. This method is very troublesome. For a large number of style deletion operations, using JavaScript can be more convenient.

2. JavaScript operation CSS

In JavaScript, we can operate CSS styles through the style attribute.

In HTML, each element has a style attribute, through which we can get or set the style of the element. Through the CSS property in the style attribute, we can set the style of the element.

For example, we use the following code to set the width of the element to 200px:

var element = document.getElementById("myElement");
element.style.width = "200px";

Of course, in addition to the style attribute, we can also use the classList attribute to manipulate CSS styles.

3. Example of deleting CSS

Next, let’s look at an example of how to use JavaScript to delete CSS.

Suppose we have a button and we need to remove its CSS style when clicked. We can achieve this through the following code:

var btn = document.getElementById("myBtn");
btn.onclick = function() {
    btn.style.display = "none";  // 将元素设置为display:none;
}

Here we use display:none; to hide the element. This is not a true delete operation, but it meets our needs.

Of course, if we want to actually remove the CSS style of the element, we can use the following code:

btn.style.backgroundColor = "";  // 将元素的backgroundColor设置为空字符串
btn.style.color = null;  // 将元素的color设置为null

Here we set the element's backgroundColor to an empty string and color to null. In this way we can delete the element's style cleanly.

4. Precautions

Of course, there are some issues that need to be paid attention to when using JavaScript to delete CSS styles. Here are some things to note:

1. If the element style is marked with !important, deleting the style requires using the CSSStyleSheet API. Many times we don't need to use the !important tag. If you don't have to use it, try not to use it.
2. When deleting CSS styles, it is best to delete each style one by one rather than deleting the style of the entire element. This ensures that only the styles that need to be deleted are deleted to avoid accidental deletion.
3. For dynamically added elements, you need to pay attention to checking whether the element exists while deleting the style. There will be problems removing the style if the element does not exist.

In short, JavaScript is a powerful scripting language that plays a very important role in front-end development. Through the examples introduced in this article, we can see that it is not difficult to use JavaScript to delete CSS styles, but there are some details that need to be paid attention to. I believe that after readers master this knowledge in practice, they will be more flexible in using JavaScript to manipulate CSS styles in front-end development.

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