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JavaScript

varlevi
varlevi
8,113 Points
Posted by varlevi
varlevi
8,113 Points

Changing the Text Color of all items with the same tag in Javascript

Hi! I need to change the color of all h3 elements on a page when the user clicks a button in vanilla javascript. I've tried loop through an array with all the h3 in it using for loops, but I'm getting an

Uncaught TypeError: Cannot read property 'style' of undefined
    at HTMLDivElement.<anonymous>

error. Here's my code:

let darkButton = document.getElementById('dark-button');
darkModeState = false;
darkButton.addEventListener('click', () => {
  darkModeState = !darkModeState;
  let h3 = document.getElementsByTagName('H3');
  if (darkModeState == true) {
    document.body.style.backgroundColor = "#111";
    document.getElementsByTagName('h1')[0].style.color = '#DDD';
    document.getElementsByTagName('h2')[0].style.color = '#DDD';
    for (i of h3) {
      h3[i].style.color = '#DDD';
    }
  } else {
    document.body.style.backgroundColor = "#FFF";
    document.getElementsByTagName('h1')[0].style.color = '#DDD';
    document.getElementsByTagName('h2')[0].style.color = '#DDD';
    for (i of h3) {
      h3[i].style.color = '#DDD';
    }
  }
})

Thanks in advance for any help!

2 Answers

Ryan Groom
Ryan Groom
18,674 Points
Ryan Groom
Ryan Groom
18,674 Points

varlevi So when you're using the for of loop, the "i" in the "i of h3" is already referencing the specific iteration of the h3 elements that you're looping through, so rather than using h3[i].style.color you would just use i.style.color! I hope this helps! if not, let me know!

Steven Parker
Steven Parker
229,708 Points
Steven Parker
Steven Parker
229,708 Points

To iterate on the indexes, use "in". Using "of" iterates on the elements themselves as Ryan mentioned.

    for (i in h3) {