javascript - How to get element by class name?

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Answer 1

The name of the DOM function is actually getElementsByClassName, not getElementByClassName, simply because more than one element on the page can have the same class, hence: Elements.

The return value of this will be a NodeList instance, or a superset of the NodeList (FF, for instance returns an instance of HTMLCollection). At any rate: the return value is an array-like object:

var y = document.getElementsByClassName('foo');
var aNode = y[0];

If, for some reason you need the return object as an array, you can do that easily, because of its magic length property:

var arrFromList = Array.prototype.slice.call(y);
//or as per AntonB's comment:
var arrFromList = [].slice.call(y);

As yckart suggested querySelector('.foo') and querySelectorAll('.foo') would be preferable, though, as they are, indeed, better supported (93.99% vs 87.24%), according to caniuse.com:

• querySelector(all)
• getElementsByClassName
• Don't use w3schools to learn something
• Refer to MDN for accurate information