javascript - What's the correct way to check return value from `querySelectorAll`? - Stack Overflow

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When using querySelectorAll, what is the correct way to check if it returned any elements?

It returns something that can't be checked for false. This doesn't seem to work:

var elements = document.querySelectorAll('.class');
if (elements) {
  // doesn't work, `elements` is always true
}

Right now I'm doing the following check via .length property:

var elements = document.querySelectorAll('.class');
if (elements.length) {
  // querySelectorAll returned DOM elements
}

Is this how you do it?

When using querySelectorAll, what is the correct way to check if it returned any elements?

It returns something that can't be checked for false. This doesn't seem to work:

var elements = document.querySelectorAll('.class');
if (elements) {
  // doesn't work, `elements` is always true
}

Right now I'm doing the following check via .length property:

var elements = document.querySelectorAll('.class');
if (elements.length) {
  // querySelectorAll returned DOM elements
}

Is this how you do it?

• javascript
• dom
• document
• selectors-api

Share Improve this question Follow asked Sep 17, 2015 at 18:53 bodacydobodacydo 79.5k9595 gold badges233233 silver badges328328 bronze badges

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2 Answers 2

Sorted by: Reset to default 6

That's correct.

document.querySelectorAll('.class') returns a non-live Node List, this will always be truthy.

Therefore you need to count the items in the list by using length to determine if there are more than 0 items.

Yes. querySelectorAll will return an array-like object, which has a length property (the actual object is a NodeList).

So,

if(elements.length > 0) {
  // you have elements
}

// and

if(element.length === 0) {
  // you don't have elements
}

The problem with doing if(elements) is that [] is truthy, meaning it will always return true:

!![] === true.

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