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JavaScript JavaScript and the DOM (Retiring) Getting a Handle on the DOM Selecting Elements with the Same Class Name

Posted by mk37
mk37
10,271 Points

honesty, i dont know why this for loop not working

trying to experiment from back to front with button color. the code looks good to me but no worky worky?

<button class="classBn">colour red</button>
<button>no colour</button>
<button class="classBn">colour red</button>
<button class="classBn">colour red</button>

  const classB = document.getElementsByClassName(`classBn`);

  for (let i = classB.length; i >= 0; i--) {
    classB[i].style.color = `red`;
  };

1 Answer

Robert Stefanic
Robert Stefanic
35,170 Points
Robert Stefanic
Robert Stefanic
35,170 Points

The problem is with this line:

  for (let i = classB.length; i >= 0; i--) {

Think about what classB.length will return. It returns the length of the array, not the last index of the array.

So when you're assigning i to classB.length, i has a value of 3, but classB[3] is undefined. Arrays start at 0 in JS, so the indexes of your array are 0, 1, and 2.

mk37
mk37
10,271 Points

thank you sir. that makes sense to me, i now added a minus 1 for i and it works perfectly.