JavaScript writing interface method

As Web applications become more and more popular, JavaScript has become an essential part of Web applications. For developers, how to use JavaScript to operate the interface well is a very important skill. This article will discuss how to write interfaces in JavaScript to help developers better master this skill.

1. Obtain DOM elements

In JavaScript, we can use the document object to obtain DOM elements in order to operate on them. Common methods for obtaining DOM elements are as follows:

1. getElementById method

This method searches for and returns the corresponding DOM element in the document based on the ID attribute of the element. object. When calling this method, pass a string parameter representing the ID of the element to be found.

As follows:

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

2. getElementsByTagName method

This method obtains the specified DOM element based on the tag name and returns a NodeList object containing all matching elements. When calling this method, pass a string parameter indicating the tag name of the element that needs to be obtained.

As follows:

let myDivs = document.getElementsByTagName("div");

3. getElementsByClassName method

This method gets the specified DOM element based on the class name and returns a NodeList object containing all matching elements. When calling this method, pass a string parameter indicating the class name of the element to be obtained.

is as follows:

let myElements = document.getElementsByClassName("myClass");

4. querySelector method

This method selects the specified DOM element based on the CSS selector and returns a NodeList object containing the selected element. . When calling this method, pass a string parameter representing the CSS selector of the selected element.

is as follows:

let myElement = document.querySelector("#myDiv");

2. Modify DOM elements

After obtaining the DOM elements, we can use JavaScript to modify the DOM elements to achieve various interactive effects. Here are some common DOM operations:

1. Modify the style of an element

You can control the appearance of an element by changing its style attribute. In JavaScript, you can access an element's style properties using the style attribute.

is as follows:

let myElement = document.getElementById("myDiv");
myElement.style.width = "200px";
myElement.style.height = "200px";
myElement.style.backgroundColor = "red";

2. Modify the content of the element

You can modify the content of the element through the .innerHTML attribute. When using the innerHTML attribute, you can assign an HTML markup string to it to modify the content of the element. As follows:

let myElement = document.getElementById("myDiv");
myElement.innerHTML = "
Hello World!
";

3. Create and modify elements

You can create new elements in the document using the document.createElement method and add them to existing elements through the appendChild method . After creating an element, you can modify it by setting its properties (such as innerText, src, href, etc.).

As follows:

let myElement = document.createElement("div");
myElement.innerText = "Hello World!";
document.body.appendChild(myElement);

3. Add event handler

You can use event handler to add events to elements. In JavaScript, event handlers can be added using the addEventListener method. The following are some common event types and corresponding handlers:

1. Click event

When the element is clicked, the click event is triggered. Click event handlers can be added to elements through the addEventListener method.

are as follows:

let myElement = document.getElementById("myDiv");
myElement.addEventListener("click", function(){
    //处理程序代码
});

2. Mouse move in/out event

When the mouse moves to the element, the mouseover event is triggered; when the mouse moves out of the element, Trigger mouseout event. These event handlers can be added to elements through the addEventListener method.

are as follows:

let myElement = document.getElementById("myDiv");
myElement.addEventListener("mouseover", function(){
    //处理程序代码
});

myElement.addEventListener("mouseout", function(){
    //处理程序代码
});

3. Keyboard events

When the user presses, releases a key, or continues to press a key, keydown, keyup and keypress event. These event handlers can be added to elements through the addEventListener method.

is as follows:

let myElement = document.getElementById("myInput");
myElement.addEventListener("keydown", function(){
    //处理程序代码
});

myElement.addEventListener("keyup", function(){
    //处理程序代码
});

myElement.addEventListener("keypress", function(){
    //处理程序代码
});

4. Summary

The above are some common methods of writing interfaces in JavaScript. Developers can learn and practice these methods to better master the operation of JavaScript interfaces and provide better support for Web application development. At the same time, you should also pay attention to minimizing the number of operations and the scope of influence of modifying the DOM when using JavaScript to operate DOM elements to improve the performance of JavaScript.

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