className only changing every other class

Question

I\'m performing a small text with JavaScript with the getElementsByClassName() and I am getting some unwanted results. I would like the script to change each CS

Answer 1

Instead of using getElementsByClassName(),
which returns a live HTMLCollection that will change as the classNames change,
you can use querySelectorAll(),
which returns a non-live NodeList that will not change.

querySelectorAll() has better IE support than getElementsByClassName() (IE8+ vs. IE9+).
It's also much more flexible since it supports CSS selectors (CSS2 for IE8+ and CSS3 for IE9+).

However, querySelectorAll() is slower than getElementsByClassName().
Keep that in mind if you're processing thousands of DOM elements.

Snippet

var blockSet = document.querySelectorAll(".block-default");
var blockSetLength = blockSet.length;

blockSet[0].className = "block-selected";
blockSet[1].className = "block-selected";
blockSet[2].className = "block-selected";
blockSet[3].className = "block-selected";
blockSet[4].className = "block-selected";
blockSet[5].className = "block-selected";
blockSet[6].className = "block-selected";
blockSet[7].className = "block-selected";

.block-default {
  width: 100px;
  height: 50px;
  background-color: green;
  border: 1px solid red;
  padding: 10px;
}
.block-selected {
  width: 100px;
  height: 50px;
  background-color: blue;
  border: 1px solid white;
  padding: 10px;
}

BLOCK1
BLOCK2
BLOCK3
BLOCK4
BLOCK5
BLOCK6
BLOCK7
BLOCK8