toggle js

document.getElementById('myButton').onclick = function() {
    this.classList.toggle('active');
}

/* var or const followed by its name */.getElementById(/* HTML element ID */);
/* var or const's name */.classList.toggle(/* Name of CSS class */);
// I hope this helps! 

function myFunction() {
  var element = document.getElementById("myDIV");

    element.classList.toggle("mystyle");
} 

var menu = document.querySelector('.menu') // Using a class instead, see note below.
menu.classList.toggle('hidden-phone');

var clicked = false;

function toggleBtnClick() {
  var img = document.getElementById('baseImg');
  if (clicked) {
    img.src = 'http://via.placeholder.com/350x150/e9e9e9/000000';
    clicked = false;
  } else {
    img.src = 'http://via.placeholder.com/350x150/3fafed/000000';
    clicked = true;
  }
}

// html <div class="parentElm" id="addActive"></div>

// js
function toggleClass(){
  // get the properties of an element
  var element = document.getElementById("addActive");
  
//  check if the element have class list
  if (element.classList) {
    // add active class if true
   element.classList.toggle("active");
  } else {
   var classes = element.className.split(" ");
   var i = classes.indexOf("active");
  }
 }

document.getElementById('myButton').onclick = function() {

    var className = ' ' + myButton.className + ' ';

    if ( ~className.indexOf(' active ') ) {
        this.className = className.replace(' active ', ' ');
    } else {
        this.className += ' active';
    }              
}