How to Check if All Values in an Array are Equal in Javascript

  • We have selected two elements button and h1 using the document.querySelector() method and stored them in btnCheck and result variables respectively.
  • We have a global variable users. users holds an array of strings.
  • We have attached the click event listener to the button element.
  • every() method takes an anonymous function as a parameter and returns a Boolean value. As you know, arrays have a 0-based index.  This anonymous function will run for each item and simply check if each item is equivalent to the first item in the array.
  • We are setting the inner text of the h1 element to the Boolean value returned by the every() method.
let btnCheck = document.querySelector('button');
let result = document.querySelector('h1');

let users = ['Peter', 'Peter'];

btnCheck.addEventListener('click', () => {
    let isEqual = users.every(user => user == users[0]);

    result.innerText = isEqual ? 'True' : 'False';