javascript - is document.getElementsByClassName faster than looping through the nodes? -

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i working on script chrome extension have check if items exist in division. , standing before dilemma having. let's first want check classnames, tags data-ng attributes , img nested directly in tag. either using:

var first = node.getelementsbyclassname('classnameofinterest');  var second = new array(); var temp = node.getelementsbytagname('a'); for(var = 0 ; < temp.length ; a++){     if(temp[a].hasattribute('data-ng')){         second.push(temp[a]);     } }temp = false;  var third = new array(); temp = node.getelementsbytagname('img'); for(var = 0 ; < temp.length ; a++){     if(temp[a].parentnode.nodename == 'a'){         third.push(temp[a]);     } }temp = false;

or going through elements of possible interest, , check them 3 conditions right away, this:

var nodes = node.getelementsbytagname("*"); var first = new array(); var second = first; var third = first; for(var = 0 ; < nodes.length ; a++){          if(nodes[a].classname.match(\b(classnameofinterest)\b))              {first.push(nodes[a]);}     else if(nodes[a].nodename == 'a' && nodes[a].hasattribute('data-ng'))              {second.push(nodes[a]);}     else if(nodes[a].nodename == 'img' && nodes[a].parentnode.nodename == 'a');              {third.push(nodes[a]);} }

which of methods faster/better, , why? want make rational code ;). please help!?


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