CODEWITHSUNDEEP
javascriptcssclass
davecave
davecave

Reputation: 4818

Adding a class with javascript, not replace

I would like the ability to add a class to an element and not replace what classes are already there.

Here is my javascript so far:

function black(body) {
var item = document.getElementById(body);
    if (item) {
        item.className=(item.className=='normal')?'black':'normal';
    }
}

That piece of javascript replaces the existing classes with black. If the class already is black then it is changed to normal.

I would like to somehow combine the script above with the script below script, which adds a class, instead of replacing all existing classes.

var item = document.getElementById("body");
item.className = item.className + " additionalclass";

Upvotes: 5

Views: 2731

Answers (3)

Smartupworld
Smartupworld

Reputation: 1

I don't know if this is what you want or not because the answers here seems complicated to me...Anyway I needed to add class name without replacing the old one, so this is how I did it..

menu.children[i].getElementsByTagName('a')[0].**classList.add('resetAfter')**;

here i used classList.add() to append classes into anchor tag.

Upvotes: 0

jfriend00
jfriend00

Reputation: 707328

Here are several plain javascript functions you can use for manipulating class names in plain javascript. It takes a little extra work in these functions to match whole class names only and avoid any extra spaces before/after classnames:

function removeClass(elem, cls) {
    var str = " " + elem.className + " ";
    elem.className = str.replace(" " + cls + " ", " ").replace(/^\s+|\s+$/g, "");
}

function addClass(elem, cls) {
    elem.className += (" " + cls);
}

function hasClass(elem, cls) {
    var str = " " + elem.className + " ";
    var testCls = " " + cls + " ";
    return(str.indexOf(testCls) != -1) ;
}

function toggleClass(elem, cls) {
    if (hasClass(elem, cls)) {
        removeClass(elem, cls);
    } else {
        addClass(elem, cls);
    }
}

function toggleBetweenClasses(elem, cls1, cls2) {
    if (hasClass(elem, cls1)) {
        removeClass(elem, cls1);
        addClass(elem, cls2);
    } else if (hasClass(elem, cls2)) {
        removeClass(elem, cls2);
        addClass(elem, cls1);
    }
}

If you wanted to toggle between the black and normal classes without affecting any other classes on the specified object, you could do this:

function black(id) {
    var obj = document.getElementById(id);
    if (obj) {
        toggleBetweenClasses(obj, "black", "normal");
    }
}

Working example here: http://jsfiddle.net/jfriend00/eR85c/

If you wanted to add the "black" class unless "normal" was already present, you could do this:

function black(id) {
    var obj = document.getElementById(id);
    if (obj && !hasClass(obj, "normal")) {
        addClass(obj, "black");
    }
}

Upvotes: 4

ajax333221
ajax333221

Reputation: 11764

In case you are not going to add/remove/toggle classes that much, I would consider using something like the code below (instead of adding 2-3 functions like jfriend00's answer).

So here is the alternative for the ones that don't like to have many functions that will not use that frequently:

function toggle(id) {
    var obj = document.getElementById(id), str, len;

    if (obj) {
        str = " " + obj.className + " ";
        len = str.length;

        str = str.replace(" normal ", " ");

        if (str.length != len) {
            str += " black";
        } else {
            str = str.replace(" black ", " ");

            if (str.length != len) {
                str += " normal";
            }
        }

        obj.className = str.replace(/^\s+|\s+$/g, "");
    }
}

It basically stores the length, tries to replace, checks if it removed the class (by comparing old and new lengths) then applies the necessary changes.

Note: it will toggle the classes perfectly with the condition that you should not have the two classes at the same time at the beginning.

DEMO

Upvotes: 0

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