JavaScript Reference
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Quick Reference

The Element getElementsByClassName() method returns a collection of child elements with a given class name.

<ul class="my_cars">
    <li class="car">Alfa Romeo</li>
    <li class="car">Porsche</li>
</ul>

<!-- button for calling the function -->
<button onclick="my_function()">Change Car</button>
// function to change the first car in the list to Maserati
function my_function() {
    let my_list = document.getElementsByClassName('my_cars')[0];
    my_list.getElementsByClassName('car')[0].innerHTML = 'Maserati';
}

Output

- Maserati
- Porsche

Syntax

element.getElementsByClassName(classname)

JavaScript Notes:

  • When using JavaScript, single or double quotation marks are acceptable and work identically to one another; choose whichever you prefer, and stay consistent
  • JavaScript is a case-sensitive language; firstName is NOT the same as firstname
  • Arrays count starting from zero NOT one; so item 1 is position [0], item 2 is position [1], and item 3 is position [2] … and so on
  • JavaScript variables must begin with a letter, $, or _
  • JavaScript variables are case sensitive (x is not the same as X)
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