Interpreting the dollar sign $ in jQuery

Title: In-depth analysis of the usage of $ symbol in jQuery

In front-end development, jQuery is a very popular and powerful JavaScript library, which provides convenience for developers , Efficient DOM operation and event processing functions. In jQuery, the $ symbol is a very important identifier, which represents the alias of the jQuery object. This article will analyze the usage of the $ symbol in jQuery in detail, and illustrate its flexibility and convenience through specific code examples.

1. The $ symbol serves as the global object of jQuery

In jQuery, the $ symbol is a global object through which you can access methods and properties in the jQuery library. The $ symbol can be understood as a concise reference symbol, which is convenient for code writing and reading. We can demonstrate the use of the $ symbol as a jQuery global object through the following code:

$(document).ready(function() {
    // 在文档加载完成后执行的代码
    console.log("Document is ready.");
});

In the above code, $(document) indicates selecting the document object, .ready( ) is a method in jQuery, used to specify the function to be executed after the document is loaded. Use the $ symbol to express this operation concisely and clearly.

2. The $ symbol serves as a jQuery selector

$ symbol also plays the role of a selector in jQuery. By combining the $ symbol with a selector expression, you can easily select DOM elements and implement Operations on page elements. The following is an example:

// 选取id为myElement的元素
var element = $("#myElement");
// 添加样式
element.css("color", "red");

In the above code, $("#myElement")selects the element with id myElement through the $ symbol and assigns it to the variable element, Then use element.css("color", "red") to add a red font color to the element.

3. $ symbol chain operation

Through the $ symbol, we can also implement chain operations, that is, continuously calling multiple jQuery methods in the same statement. This approach can simplify the code structure and improve readability. For example:

$("#myElement")
    .css("color", "blue")
    .fadeOut(1000)
    .delay(500)
    .fadeIn(1000);

In the above code, we select the element with the id myElement through the $ symbol, and then call the four methods of css, fadeOut, delay and fadeIn in order to implement a series of operations to make the element First turn blue, then fade out, delay for 0.5 seconds, then fade in.

4. $ symbol and function

In jQuery, the $ symbol can also be used to wrap functions. You can pass the function as a parameter to the $ symbol to execute a certain function after the document is loaded. operate. For example:

$(function() {
    // 在文档加载完成后执行的函数
    console.log("Document is fully loaded.");
});

In the above code, $(function() { ... }) can replace $(document).ready(function() { ... } ), the effect is the same, both execute the specified function after the document is loaded.

5. The $ symbol and AJAX requests

Finally, the $ symbol also plays the role of executing AJAX requests in jQuery, which can easily send asynchronous requests and process response data. The following is a simple example:

$.ajax({
    url: "example.com/data",
    method: "GET",
    success: function(data) {
        console.log("Data received: ", data);
    }
});

In the above code, $.ajax({...}) uses the $ symbol to initiate a GET request to example.com/ data, and printed the data after a successful response.

Through the above code examples, we have deeply analyzed the various uses of the $ symbol in jQuery: as jQuery's global object, selector, chain operation, function wrapper and AJAX request. The flexibility and convenience of the $ symbol make front-end development simpler and more efficient. I hope this article can help readers better understand and apply the use of the $ symbol in jQuery.

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