Js checks whether a simple instance of a specified control exists on the page

Source: Internet
Author: User

Js checks whether a simple instance of a specified control exists on the page

This article mainly introduces a simple example of determining whether a specific control exists on the js page. If you need a simple example, you can refer to it for help.

If (document. getElementById ('show _ pic ')! = Null) {document. getElementById ('show _ pic '). src = this. value ;}

Show_pic is an image control in the page. We must first ensure that this control exists on the page before we can operate on it. Otherwise, JS will encounter errors, so we used this method to make a judgment, I heard from netizens that there is another function in JS to determine whether the object exists. Unfortunately, I did not find it.

 

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