Im trying to add class by Javascript in a section,but this error is occurring: Cannot read properties of null (reading 'classList')

Question

// here is the function that iḿ trying to use, i've already tried to use  getElementbyID, but the same error keeps on going.

let sla = document.querySelector('#MathSection')


function mathOn() {
  
  if(sla.classList.contains('show')) {
    sla.classList.remove('show')
  } else {
    sla.classList.add('show')
  }
}

I've already tried getElementbyID, but the same error happens, I've tried to change from section to div, but the same error continues, I don't know how to proceed because I'm learning a short time ago, and I don't know how to manipulate the DOM.

You need to show us your HTML code where you include the script. Perhaps your `script` tag is added before the element? — Spectric, Nov 23 '22 at 01:01
you need to run your script after the #MathSection is created. If your html is static, there are various ways to do so: put your script at the end of your html body, document.addEventListener("DOMContentLoaded", function(event) {/* your script here*/}), add the defer attribute to your script tag — user3252327, Nov 23 '22 at 01:05
Simply moving the `let sla = ...` line into the `mathOn` function would probably solve this — Phil, Nov 23 '22 at 01:06

Im trying to add class by Javascript in a section,but this error is occurring: Cannot read properties of null (reading 'classList')

0 Answers0