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In my JavaScript, I have two elements.

I have logged the two elements and it shows the following:

Element 1:

enter image description here

Element 2:

enter image description here

The problem is:

  • When I console.log the children of each element (element.children) it obviously returns a list of elements.
  • But the weird thing is, that one element is empty (and has a length of 0), but has 3 elements (and has a length of 3) once expanded.

If you read the logs below for the children of the elements, you will understand what I am talking about...

Element 1 (this one is working as expected):

enter image description here

Element 2 (the problematic one):

enter image description here

Does anyone have any idea what is going on here? How can there be contradictory reports of the number of children?

How do I fix this? I need to loop through the children, but it won't let me because the length is apparently 0.

Thanks in advance! All help appreciated.

David Callanan
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1 Answers1

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When you log objects to the console, the object's current state is not snapshotted and displayed (as you might expect); instead, the console gets a live reference to the object. When you expand it in the console, you see its contents as of when you expand it, not as of when you logged it. More on that in this question and its answers.

So apparently your collections are empty when you do your logging, and then gain their elements later. You just want to make your code wait until the collections are populated. For instance, if you're doing this immediately when your script is run, consider putting the script at the end of the document, right before the closing </body> tag.

The very subtle blue (i) icon next to the object has a tooltip that's useful; if you hover it you see:

Tooltip saying "Object value at left was shapshotted when logged, value below was evaluated just now."

It says "Object value at left was snapshotted when logged, value below was evaluated just now."

But generally: Rather than stumbling around in the dark with a console.log torch, I suggest turning on the lights using the debugger built into your browser and/or IDE.

T.J. Crowder
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    Thanks for the help! I didn't realize that this was being called before I added elements to the html (through jscript) – David Callanan Jul 29 '16 at 14:16
  • But, how can we get the actual length of array. i.e evaluated length – Mangesh Daundkar Nov 14 '18 at 10:36
  • @MDM - The question is, evaluated *when*? When you log it? Or later when you look at the object in the console? If you want the length as of when you logged it, log `arr.length`. If you want it later, when you expand the array in the console, look at the `length` property in the display of the expanded array. – T.J. Crowder Nov 14 '18 at 10:51
  • @MangeshDaundkar you can log children nodeList of *cloned* DOM node duplicate made at the moment of call: `console.log(el.cloneNode(true).children)`. The clone lives outside document (until appended somewhere) and you'll have the only reference to it, so nothing will be able to mutate it. – myf Nov 23 '20 at 14:58
  • I too faced a similar issues while getting the dom elements in react, then to counter this I used a setTimeout function with a small time interval so that dom elment can only be accessed once it is rendered. – vaibhav naik Jan 26 '21 at 11:22
  • @vaibhavnaik - This doesn't have anything to do with whether a DOM element is rendered. Just that the state may have changed between when you log it and when you expand it in the log. – T.J. Crowder Jan 26 '21 at 11:25
  • @T.J.Crowder So whats the ideal way to use it in react. Is my workaround a bad code? – vaibhav naik Jan 26 '21 at 11:30
  • @vaibhavnaik - Just be aware of what this behavior means. If you need to know the value of an object property *as of when it was logged*, log the property, not the object as a whole. If you log the object as a whole, again, just be aware that what you see later when you look is what' there *when you look*, not when you logged it. But my general advice is: Rather than stumbling around in the dark with a `console.log` torch, *turn on the lights* using the debugger built into your browser and/or IDE. :-) – T.J. Crowder Jan 26 '21 at 11:33