A summary of how jquery determines whether an element exists

Use the traditional JavaScript method as follows:

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if (document.getElementById (' div ')) {} else {}

Using jquery is a simple matter of determining whether the element is 0 or not, and if 0, the element does not exist.

The jquery selector gets an element that returns an object regardless of whether the element exists

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var my_element=$ ("#myId");

Here, regardless of whether the element "myID" exists, My_element is always an object

Use the following method to determine if the "myID" element exists

The code is as follows:

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if ($ ("#div"). Length > 0) {//Find the element corresponding to Id=div, and then execute this block of code}

You can even find a combination of elements, such as the following, we find an ID defined as the DIV element contains IMG, the code is as follows:

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if ($ ("#div img"). Length > 0) {//Find the element that corresponds to ID=DIV and contains IMG, and then execute this block of code}

Example

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<div id= "Divbody" > <div id= "Divtest" ><div> </div>

The top is simple HTML code.

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JQuery ( Document). Ready (function () {     if (jQuery ("#divTest"). Length > 0) {    & nbsp;    jQuery ("    }     Else {         if (jQuery ("#divBody"). Length) { & nbsp;           jQuery ("#divBody"). Append (" ');        }    } });

The code above shows how to tell if an object exists. The idea of the program is: if there is a divtest this Div object, Google's logo will be placed in the Divtest ID of the DIV, otherwise put the picture in Divbody. In this case, the end result of the program places the picture in divtest because of the existence of an object divtest

Attach some other methods

The second method:

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$ ("#myId"). HTML ("abc");

If myID does not exist the above code will not be wrong, just do not do any action;

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var data=$ ("#myId"). html ();

If myID does not exist, data is a null value

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var data=$ ("#myId"). Val ();

If myID does not exist, data is undefined