Why does JavaScript's getElementsByClassName provide an object that is NOT an array?

Posted by Paragon on Stack Overflow See other posts from Stack Overflow or by Paragon
Published on 2012-06-16T15:05:09Z Indexed on 2012/06/16 15:16 UTC
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I'm trying to get a list in JavaScript (not using jQuery) of all the elements on the page with a specific class name. I therefore employ the getElementsByClassName() function as follows:

var expand_buttons = document.getElementsByClassName('expand');
console.log(expand_buttons, expand_buttons.length, expand_buttons[0]);

Note that I have three anchor elements on my page with the class 'expand'. This console.log() outputs

[] 0 undefined

Next, for kicks, I threw expand_buttons into its own array as follows:

var newArray = new Array(expand_buttons);
console.log(newArray, newArray.length);

This suddenly outputs

[NodeList[3]] 1

and I can click through the nodelist and see the attributes of the three 'expand' anchor elements on the page. It's also worth noting that I was able to get my code working in a w3schools test page.

It may also be of note that my use of document.getElementsByName actually does output (to the console) an array of elements, but when I ask for its length, it tells me 0. Similarly, if I try to access an array element using array_name[0] as normal, it outputs 'undefined', despite there clearly being an element inside of an array when I print the object to the console.

Does anybody have any idea why this might be? I just want to loop through DOM elements, and I'm avoiding jQuery at the moment because I'm trying to practice coding with vanilla JavaScript.

Thanks,

ParagonRG

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