The easiest way is to determine the element’s matching length

For example, HTML code:

<div class='mydiv'></div>

What we usually do is

if($('.mydiv').length>0)

The more reliable and error-proof approach is:

if($('.mydiv').length && $('.mydiv').length>0)
  return true;

 

Use the traditional javascript approach as follows:

if(document.getElementById('div')) {    
    //Find the corresponding element
} else {    
    //No corresponding element was found
}

Using jQuery is relatively simple. You only need to determine whether the length of this element is 0. If it is 0, this element does not exist.

if ($("#div").length > 0){
    //Find the element with the corresponding id=div, and then execute the block
}

We can even find the composite elements, as follows: we can find whether img is contained in the element whose id is defined as div. The code is as follows:

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

Isn’t that easy? You can try it out