What are the usages of javascript $

javascript $ usage: 1. [$()] can be [$(expresion)], that is, css selector, Xpath or html element; 2. [$()] can be [$(element) 】, that is, a specific DOM element.

The operating environment of this tutorial: Windows 7 system, JavaScript version 1.8.5, DELL G3 computer.

javascript $ usage:

1. The meaning of $

The author of JS application library JQUERY uses $ as a Custom function name, this function is a function to obtain the specified web page element.

function $(Nid){
return document.getElementById(Nid);
}

2. Simple usage

Here are three simple usage methods.

2.1, $(expresion)

$() can be $(expresion), that is, css selector, Xpath or html element, that is, through the above expression to match the target element.

2.2. $(element)

$() can be $(element), which is a specific DOM element. For example, commonly used DOM objects include document, location, form, etc.

2.3. $(function)

$() can be $(function), that is, a function, which is a member of $(document).ready() shorthand.

$(document).ready(function(){ 
alert("Hello world!"); 
});

can write:

$(function(){ 
alert("Hello world!"); 
});

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