Master the role of the $ symbol in jQuery

In front-end development, jQuery is a popular JavaScript library that is widely used to simplify DOM manipulation and event handling. In jQuery, the most representative symbol is the $ symbol. This article will combine specific code examples to deeply explore the importance of the $ symbol in jQuery.

1. The origin and role of the $ symbol

jQuery is a js library created by John Resig, designed to simplify the process of operating JavaScript and HTML documents, and use There are many functions and methods to achieve this goal. In jQuery, the $ symbol is used as an alias, which actually represents the global object jQuery. The $ symbol is very important in jQuery. It is the most commonly used selector and global function.

2. Basic usage of the $ symbol

In jQuery, the $ symbol is usually used for selectors and function calls. Through the $ selector, we can easily select DOM elements and operate on them, and through the $ function, we can call various methods and functions provided by jQuery. Here are some basic code examples to demonstrate the usage of the $ symbol:

// 通过$选择器选择id为"myDiv"的元素
var myDiv = $("#myDiv");

// 给选中的元素添加一个类名
myDiv.addClass("highlight");

// 给选中的元素设置背景颜色
myDiv.css("background-color", "yellow");

// 使用$函数创建一个新的<div>元素
var newElement = $("<div>This is a new element</div>");

// 将新元素添加到文档中
$("body").append(newElement);

Through the above code examples, we can see the importance of the $ symbol in jQuery sex. It simplifies the process of manipulating DOM elements and makes the code more concise and efficient.

3. Chained calls of $ symbols

In addition to basic selectors and function calls, $ symbols also support chained calls. This means that we can call multiple jQuery methods consecutively in a single statement without creating separate temporary variables for each method. This chained calling method greatly improves the readability and simplicity of the code. The following is an example:

// 通过$选择器选择class为"box"的元素，并设置样式
$(".box")
    .css("background-color", "red")
    .addClass("border")
    .fadeOut(1000);

Through chain calls, we can implement multiple operations on elements in one line of code. The code is concise and easy to understand.

4. Plug-in extension of the $ symbol

In jQuery, the $ symbol can also be used to introduce third-party plug-ins. Many jQuery plug-ins extend themselves as methods of the jQuery object, so that these plug-ins can be called directly through the $ symbols. This extension adds many extra features to jQuery, which is very convenient during development. The following is a simple plug-in extension example:

// 自定义一个简单的插件
$.fn.customPlugin = function() {
    this.css("color", "blue");
};

// 使用自定义插件
$(".box").customPlugin();

By extending the jQuery plug-in, we can add various custom functions to the project and improve development efficiency.

Conclusion

$ symbol, as the core identifier in jQuery, carries important functions and meanings. It simplifies the process of DOM operation, event handling and plug-in extension, and provides powerful tools for front-end developers. Through the specific code examples in this article, I hope readers can better understand the importance of the $ symbol and use it skillfully in actual development. The powerful functions and concise syntax of jQuery are an important embodiment of the $ symbol.

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