Jquery checks the element existence and jquery checks the element

Jquery checks the element existence and jquery checks the element

Javascript check element existence:

Even if this element is deleted, do not worry about the javascript code error;

Jquery checks the element existence:

The Code is as follows:

If (! Document. getElementById ("preview") return false;

 

 

Jquery $ ("# preview") always gets an object even if this element is not present on the webpage.

You cannot use the following code:

If ($ ("# preview "){
// Do something
}

Therefore, when jquery is used to check whether an element exists on a webpage, it should be determined based on the length of the obtained element.

The Code is as follows:

If ($ ("# preview"). length> 0 ){
// Do something
}