Question

176

What is the difference between class and classname in javascript?

rated 0 times [ 180] [ 4] / answers: 1 / hits: 31965 / 10 Years ago, sat, january 3, 2015, 12:00:00

In order to find children objects of a certain class name, I had to create my own helper function

findChildrenByTagName = function(obj, name){

    var ret = [];

    for (var k in obj.children){

        if (obj.children[k].className === name){

            ret.push(obj.children[k]);

        }

    }

    return ret;

}

An example of how it works is

var li = document.createElement('li');

var input = document.createElement('input');

input.setAttribute('class','answer_input');

li.appendChild(input);

console.log(findChildrenByTagName(li,answer_input));

However when I replace className above by class in the function above, the code doesn't work. So I am naturally wondering what the difference is between class and className. A quick search on google doesn't reveal anything.

Also what's the best way to return a list of children of a particular class name for a generic object? If such doesn't exist, is there a way to add a method to all objects so that I can call

li.findChildrenByTagName(answer_input);

instead of the global function above?

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dasias

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3 Years ago

answered 10 Years ago clarkulisesa · Accepted Answer

Let's break this into answerable parts:

Question 1:

What is the difference between class and classname in javascript?

Your title question.

Answer 1:

Class is an attribute in an html element <span class='classy'></span>

While, on the other hand, .className is a property that can by called on an element to get/set its class.

var element = document.createElement('span');

element.className = 'classy'

// element is <span class='classy'></span>

Setting the class can also be accomplished with .getAttribute('class') and .setAttribute('class', 'classy'). We change manipulate classes so often, however, that it merited its own .className method.

Question 2:

However when I replace className above by class in the function above, the code doesn't work. So I am naturally wondering what the difference is between class and className.

Answer 2: element.class is not a property.

Class may be an attribute of an element, but you can't call it like el.class. The way you do it is by el.className, like you already figured out. If you look at the MDN for Element, you'll see that elements have many properties and methods, but .class isn't one.

enter

Question 3:

Also what's the best way to return a list of children of a particular class name for a generic object?

Answer 3: Use .getElementsByClassName

Rather than using a purpose-made function, people frequently "chain" methods one-after-another to achieve your desired effect.

Based on your needs, I think you're asking for the .getElementsByClassName method. Here are the full docs and an excerpt:

The Element.getElementsByClassName() method returns returns a live HTMLCollection [array] containing all child elements which have all of the given class names.

To reuse the example from your answer:

var li = document.createElement('li');

var input = document.createElement('input');

input.setAttribute('class','answer_input');

li.appendChild(input);

console.log(li.getElementsByClassName("answer_input")[0]);

// would return the <input class='answer_input'> as the first element of the HTML array