# How to Auto Calculate form field in Javascript?

Today, We want to share with you javascript calculation form field values.In this post we will show you Real time calculation with custom fields, hear for calculate two input field values in javascript we will give you demo and example for implement.In this post, we will learn about Javascript Onchange Calculate Total Quantity Price Demo with an example.

## How to Auto Calculate Price in Javascript?

Contents

Example 1: index.html

```

How to Auto Calculate Price in Javascript - www.pakainfo.com

Number Of Items

Mobile
Pendrive
LCD
Computer
Laptop
Car
Bike
Iphone
Home
Khatri

Total Amount

function calcular(val) {
var tot_price = val * 100;
/*prints the result*/
var results = document.getElementById('item_price');
results.value = tot_price;
}

```

### Sum of 2 inputs and appear in real time

Example 2:

```
First Number:   Second Number:

```

javaScript Code

```function calcular() {
var n1 = parseInt(document.getElementById('n1').value, 10);
var n2 = parseInt(document.getElementById('n2').value, 10);
}
```

### how to auto calculate fields in inputs?

Auto calculating fields in inputs can be done using JavaScript. Here’s a basic example of how it can be done:

First, add an event listener to the input fields you want to auto-calculate. This can be done using the addEventListener() method.

```document.getElementById('input1').addEventListener('input', calculate);
```

Next, create a function that will perform the calculation based on the values entered in the input fields.

```function calculate() {
const input1 = parseFloat(document.getElementById('input1').value);
const input2 = parseFloat(document.getElementById('input2').value);

const result = input1 + input2;

document.getElementById('result').value = result;
}
```

In this example, the function retrieves the values entered in the input fields and performs a simple addition calculation. The result is then displayed in another input field.

Finally, call the calculate() function whenever the input fields are changed.

```

function calculate() {
const input1 = parseFloat(document.getElementById('input1').value);
const input2 = parseFloat(document.getElementById('input2').value);

const result = input1 + input2;

document.getElementById('result').value = result;
}

```

This code will auto-calculate the result field whenever the values of input1 and input2 are changed. You can modify the calculation and fields to suit your needs.

I hope you get an idea about javascript onchange calculate total quantity price demo.
I would like to have feedback on my infinityknow.com blog.