jquery can call methods in dom

With the rapid development of Web technology, JavaScript has become one of the necessary languages ​​for Web applications. As one of the most popular JavaScript libraries, jQuery provides developers with a set of easy-to-understand and powerful APIs for operating DOM. In jQuery, you can not only directly manipulate the attributes and styles of DOM elements, but also call methods in the DOM, allowing developers to develop web applications more conveniently and quickly.

In jQuery, we can use common DOM methods, such as addClass, removeClass, attr and other methods to operate elements and complete operations such as adding, deleting and updating elements. jQuery also provides some unique methods, such as the addClass and removeClass methods that can easily add and delete element styles, the hide and show methods can quickly hide and show elements, and the appendTo and prependTo methods can easily add child elements.

At the same time, jQuery also provides some methods that can directly call methods in the DOM and return corresponding results. For example, the width and height methods in jQuery can return the width and height of an element, while the offset and position methods can return the position of the element in the document. In addition, jQuery also provides some methods to access and modify the attributes and values ​​of elements, such as prop, val, html, and text methods.

Let’s take a closer look at how to call methods in the DOM in jQuery:

1. width and height methods

In jQuery, through width and The height method can directly get or set the width and height of the element. For example, we can get the width and height of an element in the following way:

//获取元素宽度
var width = $("#element").width();
//获取元素高度
var height = $("#element").height();

If you want to set the width and height of an element, you can pass the corresponding values ​​into the method, as shown below:

//设置元素宽度
$("#element").width(200);
//设置元素高度
$("#element").height(200);

It should be noted that the value here can be a number, a string, or a callback function. The return value of the callback function is the value to be set, as shown below:

//使用回调函数设置元素宽度
$("#element").width(function(index, width){
    return width * 2;
});

In this example , the index in the callback function is the index of the element in the collection, and width is the current width of the element. The value returned in the callback function is the new width to be set. Here, 2 times the original width is returned.

2. offset and position methods

The offset and position methods can respectively obtain the position of the element in the document and the position relative to its parent element. Similar to the width and height methods, these two methods can also pass in values ​​to set the position of the element.

//获取元素在文档中的位置
var offset = $("#element").offset();
//获取元素相对于其父元素的位置
var position = $("#element").position();

If you want to set the position of the element, you can call the method as follows:

//设置元素在文档中的位置
$("#element").offset({
    top: 100,
    left: 200
});
//设置元素相对于其父元素的位置
$("#element").position({
    top: 100,
    left: 200
});

When using these two methods to set the position of the element, the value passed in can also be a callback function. The return value of the function will be the value to be set.

3. prop and val methods

The prop and val methods can be used to access and modify the properties and values ​​of elements. Among them, the prop method is used to access and modify the attributes of the element, such as checked and disabled attributes, while the val method is used to access and modify the value of the element.

//获取元素属性值
var checked = $("input[type='checkbox']").prop("checked");
//设置元素属性值
$("input[type='checkbox']").prop("checked", true);
//获取元素值
var value = $("input[type='text']").val();
//设置元素值
$("input[type='text']").val("Hello, jQuery!");

In this example, we get the checked attribute value of a checkbox element and set it to true; we also get the value of a text box and set it to "Hello, jQuery!" .

4. html and text methods

The html and text methods can be used to get or set the HTML content and plain text content of the element. If a parameter is passed in, the corresponding value is set to the element's content; otherwise, these methods return the element's content.

//获取元素HTML内容
var html = $("#element").html();
//设置元素HTML内容
$("#element").html("<h1>Hello, jQuery!</h1>");
//获取元素纯文本内容
var text = $("#element").text();
//设置元素纯文本内容
$("#element").text("Hello, jQuery!");

It should be noted that when using the html and text methods to set element content, if the incoming parameters contain HTML tags, the html method is used; otherwise, the text method is used.

Summary

In jQuery, you can not only directly manipulate the attributes and styles of DOM elements, but also call methods in the DOM, allowing developers to develop web applications more conveniently and quickly. In this article, we introduce some commonly used methods, which should be very convenient to use in actual development. It should be noted that although jQuery can call methods in the DOM, there may be some problems in resource consumption, so it should be used reasonably according to the specific situation in actual development.

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