Modify nodes in javascript

Modify nodes in JavaScript

JavaScript is a dynamic programming language that is commonly used as a client-side scripting language in web design and development. HTML (Hypertext Markup Language) is one of the most basic languages ​​in web design. It describes the structure of web documents by using tags, and JavaScript can modify the nodes in the HTML document by accessing the objects and attributes of the HTML document.

Node is a building unit in HTML documents. It can be an element (tag), an attribute or a text node. Therefore, to modify the nodes in the HTML document, you must first understand the type of the node.

Modify element nodes

First, let’s look at how to modify element nodes. Element nodes refer to HTML tags that have a start tag and an end tag. For example, the following code:

<div id="myDiv">这是一个div标签</div>

The div tag here has an id attribute, and there is some text content in the tag. To modify this element, you can follow the following steps:

1. Get this element node object through DOM (Document Object Model).

let myDiv = document.getElementById("myDiv");

2. Modify the attributes or subnodes in the element node.

myDiv.style.backgroundColor = "red";  // 修改背景颜色
myDiv.innerHTML = "这是经过修改后的内容";  // 修改文本内容

The style attribute used here can modify the style of the element node, and the innerHTML attribute can modify the text content in the element node.

3. Reinsert the modified node into the document.

let parentDiv = myDiv.parentNode;
parentDiv.replaceChild(myDiv, myDiv); // 将修改后的节点重新插入到文档中

The replaceChild method used here can replace the original node with the modified node.

Modify attribute nodes

Let’s look at how to modify attribute nodes. Attribute nodes refer to attributes in HTML tags. For example, the following code:

<img src="image.jpg" alt="这是一张图片">

The img tag here has src and alt attributes. To modify this attribute, you can follow the following steps:

1. Get this element node object through the DOM.

let myImg = document.getElementsByTagName("img")[0];

2. Modify the value of the attribute node.

myImg.src = "new_image.jpg";  // 修改src属性的值
myImg.alt = "新的图片描述文字";  // 修改alt属性的值

The value of the attribute node is directly modified here.

Modify text nodes

Finally let’s look at how to modify text nodes. Text nodes refer to text information in HTML tags. For example, the following code:

<p>这是一段文本</p>

The p tag here contains a piece of text. To modify this text, you can follow the following steps:

1. Get the element node object through the DOM.

let myP = document.getElementsByTagName("p")[0];
let myText = myP.childNodes[0];  // 获取文本节点

2. Modify the value of the text node.

myText.nodeValue = "这是经过修改后的文本";  // 修改文本内容

After obtaining the text node here, its nodeValue attribute is directly modified.

Summary

The above is how to modify nodes in JavaScript. To modify a node, you need to obtain the corresponding node object first, and then modify the attributes or text. Through the above method, we can flexibly modify various nodes of the HTML document to achieve various web development needs.

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