jquery check element presence (recommended) _javascript tips

JavaScript checks for element existence: Even if this element is deleted, there is no concern about JavaScript code error;

jquery Check element presence:

The code is as follows:

if (!document.getelementbyid ("Preview")) return false;

jquery $ ("#preview") gets the object forever, even if there is no such element on the Web page.

You cannot use the following code:

if ($ ("#preview") {
//do something
}

So to use jquery to check if an element exists on a Web page, it should be judged by the length of the element it gets.

The code is as follows:

if ($ ("#preview"). length>0) {
//do something
}

The above is a small set to introduce the jquery check element existence of the core code, hope to help everyone, if you have any questions welcome to my message, small series will promptly reply to everyone.