How to write jquery

jQuery is a widely used JavaScript library that greatly simplifies many common web development tasks. As a web developer, it is very important to know how to write jQuery code.

In this article, we will introduce how to write jQuery code, including selecting elements, event handling, animation effects, and basic AJAX requests. We'll also demonstrate some jQuery best practices to help you write clearer, maintainable, and scalable code.

Step One: Select Elements

Selecting elements is one of the most common operations in jQuery. It allows us to easily select HTML elements and operate on them. jQuery selectors use CSS syntax, so if you are familiar with CSS, jQuery selectors will be easy to understand. Here are some common selectors:

• $('element'): Selects all elements that match the specified element name.
• $('.class'): Selects all elements matching the specified class name.
• $('#id'): Selects all elements matching the specified ID.
• $('parent>child'): Selects all elements matching the specified parent element/child element.
• $('p:first'): Select the first element in the parent element that meets the conditions.

Once elements are selected, you can perform many operations on them, such as modifying styles, binding events, or adding/removing elements, etc.

Step 2: Event Handling

Another important function of jQuery is event handling. Event handling allows us to execute code when specific user actions occur. These operations include clicks, double-clicks, mouse movements, keyboard presses, and more.

In order to handle events, we need to write event handlers. The event handler should be a function that the browser will automatically call when the event occurs. Here is an example of how to write a simple click event handler:

// jQuery选择元素
$('button').click(function () {
  console.log('Clicked!');
});

In the above example, when the user clicks the button element, the browser will automatically call the function and change the string "Clicked! "Write to the console.

Step 3: Animation effects

jQuery can also help us create various animation effects, such as fade in and fade out, sliding, expand/collapse, etc. Creating animation effects with jQuery is very simple, just call one of the following functions:

• fadeIn(): Fade the element in.
• fadeOut(): Fade out the element.
• slideDown(): Expand the element.
• slideUp(): Collapse element.
• animate(): Makes the element perform custom CSS property animation.

The following is an example of how to use the fade-in effect to dynamically display an element:

// 选择元素
$('#myElement').fadeIn();

The above code will select an element with the ID myElement and fade it in to display.

Step 4: AJAX request

AJAX is a technology that communicates with the server asynchronously, allowing web pages to dynamically load data without having to refresh the entire page. jQuery also provides a series of functions to handle AJAX requests.

Here is an example of how to use jQuery to get a URL and display it on the page:

// 发送AJAX请求
$.get('http://example.com/data', function (data) {
  $('#myElement').html(data);
});

In the above example, the $.get() function sends an AJAX request to the specified URL, And on success inject the data returned by the server into the element with ID myElement.

Best Practices

Here, we share some jQuery best practices to help you write clearer, maintainable, and scalable code.

1. Write modular code: Split the code into independent modules, each module is responsible for a specific task, and avoid global variables as much as possible.
2. Avoid duplicating code: Avoid writing duplicate code and use functions and loops to simplify your code whenever possible.
3. Cache the selector: Cache the result of the selector into a variable to avoid repeatedly selecting elements multiple times in the code.
4. Use chain calls: Use jquery's chain calls to improve the readability and simplicity of the code.
5. Avoid DOM manipulation: Where possible, minimize manipulation of the DOM. Operating the DOM multiple times will increase the load on the page and may cause performance bottlenecks.

Conclusion

In this article, we introduced how to use jQuery to select elements, handle events, create animation effects, and handle AJAX requests. We also share some jQuery best practices to help you write clearer, maintainable, and scalable code. Learning these skills can greatly improve your web development capabilities and make your work more efficient and elegant.

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