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Javascript offsetWidth returns undefined

I have a JS function that gets the width of a div on my page:

function getWidth() { var container = document.getElementsByClassName('tag'); var message = "The width of the contents width padding: " + container.width + "px.\n"; alert(message); }

The function does not start until the page loads:

 <body onload="getWidth()">

And a div is defined in CSS as a percentage, with a maximum width of 900 pixels, which should be the result. But instead, I get this warning:

 The width of the contents width padding: undefinedpx.

I was looking for an answer, but it looks like it should be work. For what reason does it not work?

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1 answer

getElementsByClassName returns a collection of nodes.

You act as if this is one thing.

You will need to select an index.

 var container = document.getElementsByClassName('tag')[0];
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Source: https://habr.com/ru/post/1497834/

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