Creating a JavaScript Function to Add Two Numbers

We can use JavaScript to create a function that will add two numbers easily. We simply need to use the addition operator + in our function. Here is the simple function to add two numbers.

function addTwoNumbers(number1,number2){
  return number1+number2;
};

And that’s it.

Our simple function called addTwoNumbers takes two parameters, the two numbers you want to add. The function just adds them together and then returns the sum.

Let’s see some examples of this function in use and the output it produces.

function addTwoNumbers(number1,number2){
  return number1+number2;
};

console.log(addTwoNumbers(2,3));
console.log(addTwoNumbers(-2,3));
console.log(addTwoNumbers(3,2));
console.log(addTwoNumbers(1092,6732));
console.log(addTwoNumbers(-22,-3));
console.log(addTwoNumbers(10002,0));

#Output
5
1
5
7824
-25
10002

Creating a JavaScript Function to Add Two Numbers Using User Input

Below is an example of how we can create a function that will add two numbers, and then execute the function when a user clicks on a button we create. We will call the JavaScript function we create using an onclick event that we will attach to the HTML button.

<p>Enter two numbers below. Click Submit to have the added value of the numbers displayed:</p>
<input id="userVal1" type="number" value1="">
<input id="userVal2" type="number" value2="">
<button onclick="addNumbers()">Submit</button>
<div id="results"></div>

Below we will write our function. Because the button has the event onclick="addNumbers()", the addNumbers() function, which we will create below, will run when the button is clicked. The function will add the two numbers that the user enters together and display the sum. If something other than a number is entered, NaN will be returned.

We will retrieve the numbers the user has entered using the value property.

function addNumbers() {
  var num1 = document.getElementById("userVal1").value;
  var num2 = document.getElementById("userVal2").value;
  var total = Number(num1) + Number(num2);
  document.getElementById("results").textContent = total;    
};

The final code and output for this example is below:

Code Output:

Full Code:

<p>Enter two numbers below. Click Submit to have the added value of the numbers displayed:</p>
<input id="userVal1" type="number" value1="">
<input id="userVal2" type="number" value2="">
<button onclick="addNumbers()">Submit</button>
<div id="results"></div>

<script>

function addNumbers() {
  var num1 = document.getElementById("userVal1").value;
  var num2 = document.getElementById("userVal2").value;
  var total = Number(num1) + Number(num2);
  document.getElementById("results").textContent = total;    
};

</script>

Hopefully this article has been useful in helping you learn how to create a JavaScript function to add two numbers.