https://www.w3schools.com/jquery/event_ready.asp

Example

Use ready() to make a function available after the document is loaded:

$(document).ready(function(){
  $("button").click(function(){
    $("p").slideToggle();
  });
});

Definition and Usage

The ready event occurs when the DOM (document object model) has been loaded.

Because this event occurs after the document is ready, it is a good place to have all other jQuery events and functions. Like in the example above.

The ready() method specifies what happens when a ready event occurs.

Tip: The ready() method should not be used together with <body onload="">.

只能在document上使用

 

.ready()

.ready( handler )Returns: jQuery

Description: Specify a function to execute when the DOM is fully loaded.

The .ready() method offers a way to run JavaScript code as soon as the page's Document Object Model (DOM) becomes safe to manipulate.

This will often be a good time to perform tasks that are needed before the user views or interacts with the page, for example to add event handlers and initialize plugins.

When multiple functions are added via successive calls to this method, they run when the DOM is ready in the order in which they are added.

As of jQuery 3.0, jQuery ensures that an exception occuring in one handler does not prevent subsequently added handlers from executing.

Most browsers provide similar functionality in the form of a DOMContentLoaded event.

However, jQuery's .ready() method differs in an important and useful way:

If the DOM becomes ready and the browser fires DOMContentLoaded before the code calls .ready( handler ), the function handler will still be executed.

In contrast, a DOMContentLoaded event listener added after the event fires is never executed.

Browsers also provide the load event on the window object.

When this event fires it indicates that all assets on the page have loaded, including images.

This event can be watched in jQuery using $( window ).on( "load", handler ).

In cases where code relies on loaded assets (for example, if the dimensions of an image are required), the code should be placed in a handler for the load event instead.

Note that although the DOM always becomes ready before the page is fully loaded, it is usually not safe to attach a load event listener in code executed during a .ready() handler.

For example, scripts can be loaded dynamically long after the page has loaded using methods such as $.getScript().

Although handlers added by .ready() will always be executed in a dynamically loaded script, the window's load event has already occurred and those listeners will never run.

jQuery offers several ways to attach a function that will run when the DOM is ready. All of the following syntaxes are equivalent:

  • $( handler )
  • $( document ).ready( handler )
  • $( "document" ).ready( handler )
  • $( "img" ).ready( handler )
  • $().ready( handler )

As of jQuery 3.0, only the first syntax is recommended; the other syntaxes still work but are deprecated. This is because the selection has no bearing on the behavior of the .ready() method, which is inefficient and can lead to incorrect assumptions about the method's behavior. For example, the third syntax works with "document" which selects nothing. The fourth syntax waits for the document to be ready but implies (incorrectly) that it waits for images to become ready.

There is also $(document).on( "ready", handler ), deprecated as of jQuery 1.8 and removed in jQuery 3.0. Note that if the DOM becomes ready before this event is attached, the handler will not be executed.

The .ready() method is typically used with an anonymous function:

$( document ).ready(function() {

  // Handler for .ready() called.

});

Which is equivalent to the recommended way of calling:

$(function() {

  // Handler for .ready() called.

});

jQuery .ready()的更多相关文章

  1. jQuery-1.9.1源码分析系列（六） 延时对象应用——jQuery.ready

    还记不记得jQuery初始化函数jQuery.fn.init中有这样是一个分支 //document ready简便写法$(function(){…}) } else if ( jQuery.isFu ...

  2. jQuery Ready 与 Window onload 的区别(转)

    “我们都知道,很多时候,在页面加载完后都需要做一些相应的初始化动作.例如,运行某些js特效,设置表单等等.怎么知道页面加载完了呢?一 般情况下都是设置body标签的onload监听window的loa ...

  3. jquery ready 延迟

    $.holdReady(true);//延迟 $.holdReady(false);//解延迟 用于下载文件的时候,异步操作 $.holdReady(true); $.getScript(" ...

  4. (十六)JQuery Ready和angularJS controller的运行顺序问题

    项目中使用了JQuery和AngularJS框架,近期定位一个问题,原因就是JQuery Ready写在了angularJS controller之前,导致JQuery选择器无法选中须要的元素(由于a ...

  5. jquery ready方法实现原理 内部原理

    jquery ready方法实现原理 内部原理 今天闲来无事研究研究jquery.ready()的内部实现,看JQ的源码一头雾水,由于自己很菜了,于是翻了翻牛人的播客,讲述详细,收获颇多. 先普及一下 ...

  6. jQuery.ready() 函数详解

    jQuery.ready() 函数详解 ready()函数用于在当前文档结构载入完毕后立即执行指定的函数. 该函数的作用相当于window.onload事件. 你可以多次调用该函数,从而绑定多个函数, ...

  7. jquery ready方法实现原理

    先看这两句代码: window.addEventListener('load',loaded,false); document.addEventListener('DOMContentLoaded', ...

  8. jquery ready和window onload区别

    window onload是指标签加载完成,并且标签资源加载完成: jquery ready是指标签加载完成,标签资源可能未加载完成 $(document).ready(function(){});= ...

  9. DOMContentLoaded vs jQuery.ready vs onload, How To Decide When Your Code Should Run

    At a Glance Script tags have access to any element which appears before them in the HTML. jQuery.rea ...

  10. JavaScript window.onload 事件和 jQuery ready 函数有何不同？

    JavaScript window.onload 事件和 jQuery ready 函数之间的主要区别是,前者除了要等待 DOM 被创建还要等到包括大型图片.音频.视频在内的所有外部资源都完全加载.如 ...

随机推荐

  1. glVertexAttribPointer 顶点数据解析方式

    glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0); 第一个参数指定从索引0开始取数据,与顶点着色器中layout(location=0)对应. ...

  2. bfs（同一最短路径）

    http://oj.jxust.edu.cn/contest/Problem?id=1702&pid=7 题意:现在有两个相同大小的地图,左上角为起点,右下角问终点.问是否存在同一条最短路径. ...

  3. docker环境下分析zookeeper观察者角色

    问题引入 zookeeper新引入的角色observer是不参与投票的,通过增加observer节点,可以在提高zk系统读吞吐量时,不影响写吞吐量. 那么问题来了 Zookeeper系统节点如果超过半 ...

  4. virtualenvwrapper安装和使用

    virtualenvwrapper安装和使用步骤: 1.安装: *nix上安装的命令: pip install virtualenvwrapper windows上安装的命令: pip install ...

  5. [LeetCode] 39. 组合总和

    题目链接 : https://leetcode-cn.com/problems/combination-sum/ 题目描述: 给定一个无重复元素的数组 candidates 和一个目标数 target ...

  6. Restful风格API中用put还是post做新增操作有什么区别？

    Restful风格API中用put还是post做新增操作有什么区别? 转 头条面试归来,有些话想和Java开发者说!>>> 这个是华为面试官问我的问题,回来我找了很多资料,想验证这个 ...

  7. 计算机体系结构总结_Pipeline

    Textbook:<计算机组成与设计——硬件/软件接口>  HI<计算机体系结构——量化研究方法>          QR 在前面一节里我们有了一块简单的RISC CPU,包括 ...

  8. jdk8中几个核心的函数式接口笔记

    1. Function接口 /** * function 接口测试 * function 函数只能接受一个参数,要接受两个参数,得使用BiFunction接口 */ public class Func ...

  9. JavaScript设计模式 样例一 —— 工厂模式

    工厂模式(Factory Pattern): 定义:定义一个创建对象的接口,但让实现这个接口的类来决定实例化哪个类.工厂方法让类的实例化推迟到子类中进行. 目的:工厂模式是为了解耦,把对象的创建和使用 ...

  10. GUI学习之二十八—QMessageBox

    今天来学习下QMessageBox. QMessageBox主要用来通知用户或者请求用户提问和接收应答一个模态对话框. 一.对话框的构成 图标是有标准图标的,可以直接调用. 我们声明的消息框,初始状态 ...