jquery - Select element by and classname in javascript

Question

I have an onChange event that needs to dynamically select an ID and then add a preset classname to pass to a function.

onChange = "show(document.getElementById(this.value). {select a class here? } );"

The equivalent in jquery

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

So how do I select an ID+classname in javascript? I know I'm being dense.

Answer 1

You need to use a classname? Ids should be unique.

var element = document.getElementById('myId');

Or say element is a parent and you want a child with a class

var elements = element.getElementsByTagName('*');

var newElements = [];

for (var i = 0, length = elements.length; i < length; i++) {

    if ((' ' + elements[i].className + ' ').indexOf(' yourClassName ') > -1) {
         newElements.push(elements[i]);
    }
}

This code basically walks through all children, and uses indexOf() to test for the presence of your class. If it finds it, it pushes it onto the new array.