Cannot use style method in JS

Question

In this code:

<header class="alg">Some text</header>
<script>
var header = document.getElementsByClassName("alg");
header.style.color = 'red';
</script>

after run it. I got from log:

TypeError: header_m.style is undefined

What do I do wrong?

Answer 1

getElementsByClassName returns multiple elements.

Therefore, you are accessing it improperly. What you want, in this case, is:

 header[0].style.color = 'red';
  //    ^ [0] will get the first element with the class, 
  // which is in this case your is header element. [1] would get the second, etc.

jsFiddle.