Add class to an element

Question

I try to write these code to make grid view through CSS:( jsbin )

var tables = document.getElementsByClassName('tableData');
var rows = tables[0].getElementsByTagName('tr');
for(var i = 1; i < rows.length; i += 2) {
  alert(rows[i]);
  rows[i].className = "alt";
}

This only works with the tr elements has class="". But if I want to add class to tr.

I've tried Core.addClass but it doesn't work.

​

Answer 1

Two years later (2012/06), there is a new and shiny approach - element.classList with methods add(), remove(), toggle(), contains().

rows[i].classList.add("alt");

Supported by

• Chrome 8+
• Firefox 3.6+
• Internet Explorer 10+
• Opera 11.50+
• Safari 5.1+