If jQuery selector return no element, then what will happen. For example, I execute the following:

$('.myclass').show();

Based on my test, it seems jQuery will check whether $('.myclass') is null, if not, then it will execute .show(), otherwise, nothing happens.

I translate the above codeline to JavaScript, as below:

document.querySelector('.myclass').style.display = 'block';

But this time if document.querySelector('.myclass') return null, there will be an error.

CodePudding user response：

If there are no matching elements, it does nothing.

If there are any matching elements, it will show all such matching elements.

It's somewhat similar to the following:

for (const elm of document.querySelectorAll(selector)) {
  elm.style.display = 'block';
}

If there are no elements matching whatever selector is, nothing happens, but no error is thrown.

Similarly, if there are no elements matching .myclass, no iteration happens, and nothing changes in the DOM, and no error is thrown.