Use javascript to add a CSS class to all elements with another class name

Question

I am trying to use javascript to add a Class to all elements with a different Class. I know you might think this is redundant but for the situation i am in it is needed. i need a way to look though all elements with that class name and add the class but I don't understand how to get a count? I am working with a cms to where I cannot change the styling in the class it self.

$(document).ready(function () {
            var ClassBtn = document.getElementsByClassName("buttonSubmit");

            ClassBtn.className = ClassBtn.className + " btn";


        });

But why? If you're adding another class to all elements with a specific class, why not just add the same behaviours to the original element-class (assuming it's for a jQuery/JavaScript behaviour), or extend/amend the style rules in the stylesheet (if it's for styling/presentation of the elements)? The question you ask is easy enough, but it seems that there's an underlying problem that might have a better solution. — David Thomas
– David Thomas, Commented Aug 18, 2013 at 1:11

Volker E. · Accepted Answer · 2015-01-02 03:29:49Z

27

Since it appears you are using jQuery:

Live Demo

$(document).ready(function () {
    $('.buttonSubmit').addClass('btn'); 
});

Without jQuery:

Live Demo

window.onload = function() {
    var buttons = document.getElementsByClassName("buttonSubmit"),
        len = buttons !== null ? buttons.length : 0,
        i = 0;
    for(i; i < len; i++) {
        buttons[i].className += " btn"; 
    }
}

edited Jan 2, 2015 at 3:29

Volker E.

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answered Aug 18, 2013 at 1:05

Brandon J. Boone

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2 Comments

phhu Over a year ago

In ES6, this works: [ ...document.getElementsByClassName("buttonSubmit") ].forEach( x => x.className += ' btn' )

phhu Over a year ago

... or alternatively, using classList and querySelectorAll: document.querySelectorAll('.buttonSubmit').forEach(x=>x.classList.add('hidden'))

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