How do I add a class name to Javascript string?

Question

I'm a JS newbie trying to alter the following code. It looks like it's adding style attributes. I would like to add the class name "reveal" to this string or below. What would that syntax look like? Many thanks for your help, guys!

 inline = ( elem.domEl.getAttribute( 'style' ) ) ? elem.domEl.getAttribute( 'style' ) + 
'; visibility: visible; ' : 'visibility: visible; '

This is a ternary condition - if the style attribute exists, assign the style attribute + visibility: visible;, else, just return visibility:visible. You can't add a class to this.\ — tymeJV
– tymeJV, Commented Nov 27, 2014 at 5:25
I think he is talking about the DOM element at elem.domE1 which seems to exist according to his provided code. — Ryan
– Ryan, Commented Nov 27, 2014 at 5:25

Leo · Accepted Answer · 2014-11-27 08:35:01Z

5

(I guess) the HTML may look like this:

<div class="some other">

In such case, if you do it like

elem.domEl.className = 'reveal';

then you'll get

<div class="reveal">

All styles brought by class some and other are gone! You definitely don't want that, right? Also you don't want repeated classname, something like

<div class="reveal reveal">

So, here are the solutions:

The best way is to use HTML5 API classList:

elem.domEl.classList.contains('reveal') // Check whether element has a classname
elem.domEl.classList.add('reveal') // Add a classname
elem.domEl.classList.remove('reveal') // Remove a classname
elem.domEl.classList.toggle('reveal') // Toggle a classname

If you still want to run the code in out-dated browsers, try these:

// Check whether element has a classname
function hasClass(ele, cls) {
    var clsChecker = new RegExp("\\b" + cls + "\\b");
    return clsChecker.test(ele.className);
}
// Add a classname
function addClass(ele, cls) {
    var clsChecker = new RegExp("\\b" + cls + "\\b");
    if(clsChecker.test(ele.className)) {
        // ele already has the className, don't need to do anything
        return;
    }
    ele.className += (' '+ cls);
}

// Remove a classname
function removeClass(ele, cls) {
    var clsChecker = new RegExp("\\b" + cls + "\\b");
    if(clsChecker.test(ele.className)) {
        // ele does have the className, remove them all (in case repeated)
        ele.className.split(clsChecker).join('');
    }
}

// Toggle a classname
function toggleClass(ele, cls) {
    var clsChecker = new RegExp("\\b" + cls + "\\b");
    if(clsChecker.test(ele.className)) {
        // ele does have the className, remove them all (in case repeated)
        ele.className.split(clsChecker).join('');
    } else {
        // ele doesn't have the classname, add it
        ele.className += (' '+ cls);
    }
}

// Usages
hasClass(elem.domEl, 'reveal') // Check whether element has a classname
addClass(elem.domEl, 'reveal') // Add a classname
removeClass(elem.domEl, 'reveal') // Remove a classname
toggleClass(elem.domEl, 'reveal') // Toggle a classname

edited Nov 27, 2014 at 8:35

answered Nov 27, 2014 at 7:59

Leo

13.9k5 gold badges47 silver badges64 bronze badges

Sign up to request clarification or add additional context in comments.

10 Comments

user2749195 Over a year ago

This is awesome! Many thanks! Is there a way to slightly delay the .classList function?

Leo Over a year ago

What do you mean by slightly delay? I didn't get the question, can you please describe the purpose?

user2749195 Over a year ago

Basically this function is adding visibility:visible and the class reveal to the element at the same time. I would like to add some time between each action so it animates to being visible, then animates with reveal attributes.

Leo Over a year ago

Then you should try opacity. Say, your element is a <p>, in CSS add these selectors p {transition: opacity 500ms linear; opacity: 0;} .reveal {opacity: 1;} Then toggle the classname reveal.

Leo Over a year ago

There's an event called 'transitionend', it is dispatched when a style transition is finished. You could listen to the event like this: elem.domEl.addEventListener('transitionend', function(e) { /* things you want to do here */ }).

|

Ryan · Accepted Answer · 2014-11-27 05:23:59Z

1

The easiest way to do it would be to just modify the Element.className property. If by saying "add class" you mean to push back a class name (string) to the element regardless of the current class name (string), then this code would do the job.

elem.domEl.className = elem.domEl.className + ' ' + <YOUR_STRING_HERE>

answered Nov 27, 2014 at 5:23

Ryan

14.7k9 gold badges68 silver badges104 bronze badges

Comments

ArinCool · Accepted Answer · 2014-11-27 05:30:27Z

1

Use:

elem.domEl.setAttribute("class", "reveal");

answered Nov 27, 2014 at 5:30

ArinCool

1,7581 gold badge13 silver badges24 bronze badges

Comments

Diptendu · Accepted Answer · 2014-11-27 05:25:59Z

0

You need to write

inline = ( elem.domEl.getAttribute( 'style' ) ) ? elem.domEl.getAttribute( 'style' ) + '; visibility: visible; ' : 'visibility: visible; '

elem.domEl.className = "reveal";

The catch here is classname is not a style attribute, its an element property.

answered Nov 27, 2014 at 5:25

Diptendu

2,1581 gold badge17 silver badges30 bronze badges

Comments

Bhojendra Rauniyar · Accepted Answer · 2014-11-27 05:26:16Z

0

May be you want to do like below:

inline = (elem.domEl.style.visibility == 'visible') ? 'hidden' : 'visible';

But if you just want to set the visible css then do this way:

elem.domEl.style.visibility = 'visible';

answered Nov 27, 2014 at 5:26

Bhojendra Rauniyar

86k36 gold badges179 silver badges241 bronze badges

Comments

The Alpha · Accepted Answer · 2014-11-27 05:39:37Z

0

You may try this:

inline = ( elem.domEl.getAttribute( 'class' ) ) ? elem.domEl.getAttribute( 'class' ) + ' classname ' : 'classname '

Also this is possible:

var cls = elem.domEl.className;
elem.domEl.className = cls ? cls + ' classname' : 'classname';

edited Nov 27, 2014 at 5:39

answered Nov 27, 2014 at 5:24

The Alpha

147k30 gold badges294 silver badges313 bronze badges

Collectives™ on Stack Overflow

How do I add a class name to Javascript string?

6 Answers 6

So, here are the solutions:

10 Comments

Comments

Comments

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

6 Answers 6

So, here are the solutions:

10 Comments

Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related