what best proceed loops javascript

i have stumbled several methods looping javascript, i many is:

for(var i = 0; i < a.length; i++){
    var component = a[i];
}

but tested here (), should substantially combined length wholly distributed once.

in jquery there .each hang function. i small better, since i don't have form array twice, above solution.

if javascript upheld macros square cake play your own, nonetheless sadly does not.

so guys use?

code1