ready meaning in javascript

JavaScript is an essential language in front-end development. It can help achieve dynamic effects on website pages and improve the interactivity and friendliness of the page. In JavaScript, there is a very important function, that is the ready() function.

ready() The function can be understood as a document ready event, which can also be called DOMContentLoaded. It is one of the most commonly used events in JavaScript. The ready() function will not be triggered until the page has loaded the HTML and CSS files, so DOM elements can be safely manipulated in the ready() function, which avoids An error caused by executing the script before it is fully loaded.

In jQuery, the ready() function is called $(document).ready(). We can use this function to execute some initialization code, such as Bind events, set styles, etc. Here is a simple example that shows how to bind a button click event in the ready() function:

$(document).ready(function() {
  $("#my-button").click(function() {
    // 点击按钮后执行的代码
  });
});

In the above code, we use $() function to select the button element, and use the click() function to bind a click event handler to the button. Since these codes are executed in the ready() function, we can safely select and manipulate DOM elements without worrying about the page not loading completely.

In addition to the $(document).ready() function, window.onload is also a very important event. Different from ready(), in window.onload, all resources (including pictures and media files, etc.) have been loaded, which means that they are executed in this event Scripts may cause page loading to slow down, so it is recommended to use the window.onload event as little as possible.

In modern web development, we usually use the modular JavaScript development model, such as using tools such as Require.js or webpack. In this development mode, we can use the define() function to define the module, and use the ready() function in the module to perform initialization operations after the module is loaded. Here is a simple example showing how to use the ready() function in a module:

define(['jquery'], function($) {
  $(function() {
    // 在模块加载完成后执行的代码
  });
});

In the above code, we use the define() function definition A module named my-module is created, in which we use the $(function() {...}) function to define the ready() function.

In summary, the ready() function is a very important function in JavaScript. It is used to perform some initialization operations after the page has loaded the HTML and CSS files. When using the ready() function, we can safely manipulate DOM elements and avoid errors caused by executing scripts before the page is fully loaded.

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