How to Add Multiple Variables in Javascript

In this tutorial, you will learn how to add multiple variables in javascript. Sometimes a word or string is meaningless and needs to be combined with another string or strings to have any significance. For a newbie developer, it can be a bit tricky to add multiple variables.

There are numerous ways to add multiple variables. But for the sake of simplicity, we will make use of addition operator (+) which helps in concatenating two or more strings. When addition operator is used with numbers, it will give you the sum of numbers.

In the following example, we have three global variables that are holding a string value. Upon click of a button, we will add multiple variables and display the result on the screen.  Please have a look over the code example and the steps given below.


  • We have 3 elements in the HTML file (div, button, and h1). The div element is just a wrapper for the rest of the elements.
  • The innerText for the button element is “Add” and for the h1 element, it is “Result”.
  • We have done some basic styling using CSS and added the link to our style.css stylesheet inside the head element.
  • We have also included our javascript file script.js with a script tag at the bottom.
<!DOCTYPE html>
<html lang="en">

  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <link rel="stylesheet" href="style.css">


  <div class="container">    

  <script src="script.js"></script>

.container {        
    text-align: center;

button {
  margin-top: 10px;
  padding: 10px 20px;


  • We have selected the button element and h1 element using the document.querySelector() method and stored them in btnAdd and output variables respectively.
  • We have two global variables firstName and lastName. They both hold a string as a value.  The third variable space holds just a blank space.
  • We have attached a click event listener to the button element.
  • In the event handler function, we are concatenating all three variablesfirstName, lastName, and space variables using addition operator (+) .
  • We are storing the final string in the result variable.
  • We are displaying the result in the h1 element using the innerText property.
let btnAdd = document.querySelector("button");
let output = document.querySelector("h1");

let firstName = `Garry`;
let lastName = `Simmons`;
let space= " ";
btnAdd.addEventListener("click", () => {  
  let result = firstName + space + lastName;
  output.innerText = result;