JavaScript allows us to retrieve an element by its id using the following syntax:
var x = document.getElementById("by_id");
I attempted to get an element by class with the following code:
var y = document.getElementByClass("by_class");
Unfortunately, this resulted in an error:
getElementByClass is not a function
Is there a way to obtain an element by its class?
The correct name of the DOM function is getElementsByClassName, not getElementByClassName. This is because multiple elements on a page can have the same class, hence the plural in "Elements".
The result of this function will be a NodeList instance, or a type that extends NodeList (such as HTMLCollection in Firefox). In any case, the result is an array-like object:
var y = document.getElementsByClassName('foo');
var aNode = y[0];
If you require the return object to be an actual array, it can easily be converted using its length property:
var arrFromList = Array.prototype.slice.call(y);
//or alternatively:
var arrFromList = [].slice.call(y);
As recommended by yckart, using querySelector('.foo') and querySelectorAll('.foo') is more preferable due to better browser support (93.99% vs 87.24%), according to caniuse.com:
Consider using either querySelector('.foo') or querySelectorAll('.foo') instead of getElementsByClassName as they offer better browser compatibility.
If you need to select elements by their class name, you can utilize the
document.getElementsByClassName('class_name');It's important to remember that the returned value is an array of elements. To access the first element, use:
document.getElementsByClassName('class_name')[0]UPDATE
Alternatively, you can now use:
document.querySelector(".class_name")class_name (if none exist, null will be returned)
or
document.querySelectorAll(".class_name")class_name (an empty NodeList will be returned if there are no elements with this class name on the page).
Utilizing
getElementsByClassName
If you have various elements with the class name 'test' applied, you can retrieve those elements like this:
var tests = document.getElementsByClassName('test');
This will return an instance of NodeList, or its larger version: HTMLCollection (FF).
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