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jquery extension methods and instance methods

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May 23, 2023 am 11:44 AM

In front-end development, jQuery is a very popular JavaScript library. Its powerful features and ease of use make many developers choose to use it to operate web pages. jQuery provides a series of instance methods and extension methods, which can provide developers with a more efficient programming experience and make the code more concise. This article will introduce jQuery's extension methods and instance methods, and provide some examples to demonstrate their use.

1. Instance methods of jQuery

In jQuery, instance methods refer to methods that can be directly called by the DOM element selected through the selector. These methods are called methods of the jQuery object. The following are some commonly used instance methods:

.addClass() method

This method can add one or more CSS class names to the selected element, as shown below ：

$('选中的元素').addClass('class1 class2');

.removeClass() method

This method can remove one or more CSS class names from the selected element, as shown below:

$('选中的元素').removeClass('class1 class2');

.attr() method

This method can get or set the attribute value of the selected element, as shown below:

// 获取属性值
$('选中的元素').attr('属性名')

// 设置属性值
$('选中的元素').attr('属性名', '属性值')

.css( )Method

This method can get or set the style value of the selected element, as shown below:

// 获取样式值
$('选中的元素').css('样式名')

// 设置样式值
$('选中的元素').css('样式名', '样式值')

.html()Method

This method can get or set the HTML content of the selected element, as shown below:

// 获取HTML内容
$('选中的元素').html()

// 设置HTML内容
$('选中的元素').html('HTML内容')

.on() method

This method can add event listening for the selected element Object, as shown below:

$('选中的元素').on('事件名', function(event) {
  // 处理事件
})

2. jQuery’s extension method

Extension method refers to a method that can be called directly on the jQuery object ($), called a jQuery function (or global function ).

$.extend() method

This method can merge one or more objects into one object, as shown below:

$.extend(target, object1, object2)

where , target is the target object to be merged, and object1, object2, etc. are the source objects to be merged.

$.ajax() method

This method is used to send HTTP requests. It allows getting data from the backend API asynchronously, and can handle callback functions after success or failure, as follows:

$.ajax({
  url: 'url',
  method: 'GET',
  data: 'data',
  dataType: 'json',
  success: function(response) {
    // 处理响应数据
  },
  error: function(jqXHR, textStatus, errorThrown) {
    // 处理请求错误
  }
})

$.getJSON() method

This method is used to send a GET request and obtain response data in JSON format. Compared with the $.ajax() method, the $.getJSON() method is simpler and has less code, as shown below:

$.getJSON('url', function(response) {
  // 处理响应数据
})

4. Example demonstration

is given below An example that demonstrates how to use jQuery's extension methods and instance methods to handle a simple example.

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>jQuery实例和拓展方法演示</title>
</head>
<body>

  <!-- 示例DOM元素 -->
  <div id="example">
    <p>jQuery实例和拓展方法演示</p>
  </div>

  <script src="https://cdn.bootcss.com/jquery/3.3.1/jquery.min.js"></script>
  <script>

    // 使用实例方法
    $('#example').addClass('test');
    $('#example').on('click', function() {
      alert('点击了example元素');
    });

    // 使用拓展方法
    var settings = {
      url: 'https://randomuser.me/api/',
      method: 'GET',
      dataType: 'json'
    };
    $.ajax(settings).done(function(response) {
      var $paragraph = $('<p>').text('随机用户：' + response.results[0].name.first);
      $('#example').append($paragraph);
    });

  </script>
</body>
</html>

In this example, the instance method is first used to add a "test" class to the element with the id "example" and bind a click event. Then, use the extension method to send a GET request, obtain the data of a random user, and display it on the page.

Summary

This article introduces the concepts and usage of jQuery's extension methods and instance methods, and provides some examples to demonstrate their usage. Whether we use instance methods or extension methods, they can help us complete front-end development tasks faster and more conveniently and improve development efficiency.

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