Remove all classes that begin with a certain string

I have a div with id="a" that may have any number of classes attached to it, from several groups. Each group has a specific prefix. In the javascript, I don't know which class from the group is on the div. I want to be able to clear all classes with a given prefix and then add a new one. If I want to remove all of the classes that begin with "bg", how do I do that? Something like this, but that actually works:

$("#a").removeClass("bg*");

Answers:

Answer

With jQuery, the actual DOM element is at index zero, this should work

$('#a')[0].className = $('#a')[0].className.replace(/\bbg.*?\b/g, '');
Answer

An approach I would use using simple jQuery constructs and array handling functions, is to declare an function that takes id of the control and prefix of the class and deleted all classed. The code is attached:

function removeclasses(controlIndex,classPrefix){
    var classes = $("#"+controlIndex).attr("class").split(" ");
    $.each(classes,function(index) {
        if(classes[index].indexOf(classPrefix)==0) {
            $("#"+controlIndex).removeClass(classes[index]);
        }
    });
}

Now this function can be called from anywhere, onclick of button or from code:

removeclasses("a","bg");
Answer

Prestaul's answer was helpful, but it didn't quite work for me. The jQuery way to select an object by id didn't work. I had to use

document.getElementById("a").className

instead of

$("#a").className
Answer

In one line ... Removes all classes that match a regular expression someRegExp

$('#my_element_id').removeClass( function() { return (this.className.match(/someRegExp/g) || []).join(' ').replace(prog.status.toLowerCase(),'');});
Answer

A regex splitting on word boundary \b isn't the best solution for this:

var prefix = "prefix";
var classes = el.className.split(" ").filter(function(c) {
    return c.lastIndexOf(prefix, 0) !== 0;
});
el.className = classes.join(" ").trim();

or as a jQuery mixin:

$.fn.removeClassPrefix = function(prefix) {
    this.each(function(i, el) {
        var classes = el.className.split(" ").filter(function(c) {
            return c.lastIndexOf(prefix, 0) !== 0;
        });
        el.className = $.trim(classes.join(" "));
    });
    return this;
};

2018 ES6 Update:

const prefix = "prefix";
const classes = el.className.split(" ").filter(c => !c.startsWith(prefix));
el.className = classes.join(" ").trim();
Answer

I've written a simple jQuery plugin - alterClass, that does wildcard class removal. Will optionally add classes too.

$( '#foo' ).alterClass( 'foo-* bar-*', 'foobar' ) 
Answer

You don't need any jQuery specific code to handle this. Just use a RegExp to replace them:

$("#a").className = $("#a").className.replace(/\bbg.*?\b/g, '');

You can modify this to support any prefix but the faster method is above as the RegExp will be compiled only once:

function removeClassByPrefix(el, prefix) {
    var regx = new RegExp('\\b' + prefix + '.*?\\b', 'g');
    el.className = el.className.replace(regx, '');
    return el;
}
Answer

Using 2nd signature of $.fn.removeClass :

// Considering:
var $el = $('<div class="  foo-1 a b foo-2 c foo"/>');

function makeRemoveClassHandler(regex) {
  return function (index, classes) {
    return classes.split(/\s+/).filter(function (el) {return regex.test(el);}).join(' ');
  }
}

$el.removeClass(makeRemoveClassHandler(/^foo-/));
//> [<div class=?"a b c foo">?</div>?]
Answer

http://www.mail-archive.com/[email protected]/msg03998.html says:

...and .removeClass() would remove all classes...

It works for me ;)

cheers

Answer

I was looking for solution for exactly the same problem. To remove all classes starting with prefix "fontid_" After reading this article I wrote a small plugin which I'm using now.

(function ($) {
        $.fn.removePrefixedClasses = function (prefix) {
            var classNames = $(this).attr('class').split(' '),
                className,
                newClassNames = [],
                i;
            //loop class names
            for(i = 0; i < classNames.length; i++) {
                className = classNames[i];
                // if prefix not found at the beggining of class name
                if(className.indexOf(prefix) !== 0) {
                    newClassNames.push(className);
                    continue;
                }
            }
            // write new list excluding filtered classNames
            $(this).attr('class', newClassNames.join(' '));
        };
    }(fQuery));

Usage:

$('#elementId').removePrefixedClasses('prefix-of-classes_');
Answer

For modern browsers:

let element = $('#a')[0];
let cls = 'bg';

element.classList.remove.apply(element.classList, Array.from(element.classList).filter(v=>v.startsWith(cls)));
Answer

I know it's an old question, but I found out new solution and want to know if it has disadvantages?

$('#a')[0].className = $('#a')[0].className
                              .replace(/(^|\s)bg.*?(\s|$)/g, ' ')
                              .replace(/\s\s+/g, ' ')
                              .replace(/(^\s|\s$)/g, '');
Answer

I also use hyphen'-' and digits for class name. So my version include '\d-'

$('#a')[0].className = $('#a')[0].className.replace(/\bbg.\d-*?\b/g, '');
Answer
(function($)
{
    return this.each(function()
    {
        var classes = $(this).attr('class');

        if(!classes || !regex) return false;

        var classArray = [];

        classes = classes.split(' ');

        for(var i=0, len=classes.length; i<len; i++) if(!classes[i].match(regex)) classArray.push(classes[i]);

        $(this).attr('class', classArray.join(' '));
    });
})(jQuery);
Answer
$("#element").removeAttr("class").addClass("yourClass");

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