classname - How do I add a class name to Javascript string? -

i'm js newbie trying alter following code. looks it's adding style attributes. add class name "reveal" string or below. syntax like? many help, guys!

 inline = ( elem.domel.getattribute( 'style' ) ) ? elem.domel.getattribute( 'style' ) +  '; visibility: visible; ' : 'visibility: visible; ' 

(i guess) html may this:

<div class="some other"> 

in such case, if like

elem.domel.classname = 'reveal'; 

then you'll get

<div class="reveal"> 

all styles brought class some , other gone! don't want that, right? don't want repeated classname, like

<div class="reveal reveal"> 

so, here solutions:

the best way use html5 api classlist:

elem.domel.classlist.contains('reveal') // check whether element has classname elem.domel.classlist.add('reveal') // add classname elem.domel.classlist.remove('reveal') // remove classname elem.domel.classlist.toggle('reveal') // toggle classname 

if still want run code in out-dated browsers, try these:

// check whether element has classname function hasclass(ele, cls) {     var clschecker = new regexp("\\b" + cls + "\\b");     return clschecker.test(ele.classname); } // add classname function addclass(ele, cls) {     var clschecker = new regexp("\\b" + cls + "\\b");     if(clschecker.test(ele.classname)) {         // ele has classname, don't need         return;     }     ele.classname += (' '+ cls); }  // remove classname function removeclass(ele, cls) {     var clschecker = new regexp("\\b" + cls + "\\b");     if(clschecker.test(ele.classname)) {         // ele have classname, remove them (in case repeated)         ele.classname.split(clschecker).join('');     } }  // toggle classname function toggleclass(ele, cls) {     var clschecker = new regexp("\\b" + cls + "\\b");     if(clschecker.test(ele.classname)) {         // ele have classname, remove them (in case repeated)         ele.classname.split(clschecker).join('');     } else {         // ele doesn't have classname, add         ele.classname += (' '+ cls);     } }  // usages hasclass(elem.domel, 'reveal') // check whether element has classname addclass(elem.domel, 'reveal') // add classname removeclass(elem.domel, 'reveal') // remove classname toggleclass(elem.domel, 'reveal') // toggle classname