change background color for all elements with the same class by hovering one

hoverbyclass.js

function hoverByClass(classname,colorover,colorout="transparent"){
	var elms=document.getElementsByClassName(classname);
	for(var i=0;i<elms.length;i++){
		elms[i].onmouseover = function(){
			for(var k=0;k<elms.length;k++){
				elms[k].style.backgroundColor=colorover;
			}
		};
		elms[i].onmouseout = function(){
			for(var k=0;k<elms.length;k++){
				elms[k].style.backgroundColor=colorout;
			}
		};
	}
}


// init / set colors for classes
hoverByClass("classname1","yellow");
hoverByClass("classname2","#c5c5c5");