The difference between jquery object and Dom object and its transformation

jquery objects are objects that are produced after wrapping a DOM object through jquery.

DOM objects can use the methods in JS

jquery objects cannot use methods in DOM objects;

As an example:

$ ("#foo"). html ();//This is the way of jquery.

Equivalent to the following

document.getElementById ("foo"). innerhtml;//this is the JS method;

1.jQuery objects converted to DOM objects

(1) The JQuery object is an array-like object that can be passed "index" and get (index).

var $cr =$ ("#fd");//jquery Object

var cr= $cr [0];//dom Object

(2) Get (index) method to get the corresponding DOM object

var $cr =$ ("#fd");//jquery Object

var cr= $cr. Get (0);//dom Object

2.DOM objects converted to jquery objects

var Cr=document.getelementbyid (' Cr ');//dom object

var $cr =$ (CR);//jquery Object

Attention:

$ (' #cr ') gets the object forever, even if the element is not on the page. Therefore, when you want to use jquery to check whether an element exists on a Web page, you cannot use the following code directly:

if ($ (' #cr ')) {

Do

}

Instead, it should be judged based on the length of the obtained element, the code is as follows:

if ($ (' #cr '). length>0) {//do}

or converted to a DOM object to judge, the code is as follows:

if ($ ("#cr") [0]) {//do}

The difference between jquery object and Dom object and its transformation