jquery - Select element by and classname in javascript -

i have onchange event needs dynamically select id , add preset classname pass function.

onchange = "show(document.getelementbyid(this.value). {select class here? } );" 

the equivalent in jquery

$('#'+this.value+'.myclassname').function(); 

so how select id+classname in javascript? know i'm being dense.

you need use classname? ids should unique.

var element = document.getelementbyid('myid'); 

or element parent , want child class

var elements = element.getelementsbytagname('*');  var newelements = [];  (var = 0, length = elements.length; < length; i++) {      if ((' ' + elements[i].classname + ' ').indexof(' yourclassname ') > -1) {          newelements.push(elements[i]);     } } 

this code walks through children, , uses indexof() test presence of class. if finds it, pushes onto new array.