Tutorials Tonight
Follow Us

JavaScript Number Format


In the article javascript number format, you will learn how to format numbers in JavaScript using some built-in and custom functions. We also work on precision and rounding of numbers.

In JavaScript, we do not have integer, float, or double data types for numbers like in Java, C, or C++.

Instead, JavaScript uses a Number data type which is always double. the number data type is used to represent numeric values. It can be used to represent both integer and floating-point numbers.

While programming we generally face situations like converting a long float value to a precision of 2 or 3. Like 3.141592 => 3.14.

And sometimes you have to convert a general big number into a comma-separated number like 1000000000 => 1,000,000,000 or convert a number to some currency system, like 100 => $100.

These problems are shown in the image below and can be solved by formatting numbers.

javascript number format

    Table Of Contents

  1. JavaScript Number Format To Decimal
  2. Separating number by comma
  3. Currency Format
  4. Conclusion

Decimal Precision Number Format

While doing some complex calculations our number is generally in a long decimal format which is not very readable. So we need to convert it into a more readable format by pressing the number of decimal places.

JavaScript provides a built-in method Number.toFixed() to format a number to a specified number of decimal places.

The toFixed() method takes 1 argument which is the number of decimal places to be precise.

Example

let num = 12.345678;

// default toFixed() method
console.log(num.toFixed()); // 12
// 2 decimal places
console.log(num.toFixed(2)); // 12.35
// 3 decimal places
console.log(num.toFixed(3)); // 12.346
// 6 decimal places
console.log(num.toFixed(4)); // 12.3457

You can also expand the number by giving a large number fixed place value.

Example

let num = 34.567;

console.log(num.toFixed(5)); // 34.56700
console.log(num.toFixed(10)); // 34.5670000000

JavaScript Number Format Comma

To format a number with a comma means to separate the number by a comma at every 3rd digit like 123456789 => 1,234,567,890 to be more readable for system million, billion, trillion, etc.

Another style of separating number is by placing comma at like 123456789 => 1,23,45,67,890.

Built-in Method for comma separation

These formats can be achieved by using the toLocaleString() method.

It accepts 2 optional arguments: locale and options.

the default value of locale is en-US.

The locale can be any of the following:

Example

let num = 7323452568.283;

// US system en-US
console.log(num.toLocaleString('en-US')); // 7,323,452,568.283

// India system hi-IN
console.log(num.toLocaleString('hi-IN')); // 7,32,34,52,568.283

The position of the comma can be changed by different locales like the 'en-US' separates numbers with a comma at every 3 digits while 'hi-IN' uses a comma at every 2 digits (the last 3 digits are not separated).


Custom Function For Comma Separation

You can also create your own custom function that takes a number and returns a comma-separated number.

Our function will accept a number and return a comma-separated number at every 3 digits.

The steps to create the function are as follows:

  1. Check if the number is decimal. If it is decimal, then take digits before the decimal point because we only need to place a comma before the decimal point.
  2. Check if the number is negative. If it is negative, then remove the sign for now.
  3. Create a loop to iterate through the number and place a comma at every 3 digits.
  4. Add sign back if it was negative. Also, add a decimal point and decimal digits if it was decimal.
  5. Finally, return the number.

Example

function separateComma(val) {
  // remove sign if negative
  var sign = 1;
  if (val < 0) {
    sign = -1;
    val = -val;
  }
  // trim the number decimal point if it exists
  let num = val.toString().includes('.') ? val.toString().split('.')[0] : val.toString();
  let len = num.toString().length;
  let result = '';
  let count = 1;

  for (let i = len - 1; i >= 0; i--) {
    result = num.toString()[i] + result;
    if (count % 3 === 0 && count !== 0 && i !== 0) {
      result = ',' + result;
    }
    count++;
  }

  // add number after decimal point
  if (val.toString().includes('.')) {
    result = result + '.' + val.toString().split('.')[1];
  }
  // return result with - sign if negative
  return sign < 0 ? '-' + result : result;
}

let num1 = 12345678;
console.log(separateComma(num1));

// decimal number
let num2 = -723694769.2343;
console.log(separateComma(num2));

The same function can be created using the regular expression and replace method.

Example

function commaSeparateNumber(val) {
  // remove sign if negative
  var sign = 1;
  if (val < 0) {
    sign = -1;
    val = -val;
  }

  // trim the number decimal point if it exists
  let num = val.toString().includes('.') ? val.toString().split('.')[0] : val.toString();

  while (/(\d+)(\d{3})/.test(num.toString())) {
    // insert comma to 4th last position to the match number
    num = num.toString().replace(/(\d+)(\d{3})/, '$1' + ',' + '$2');
  }

  // add number after decimal point
  if (val.toString().includes('.')) {
    num = num + '.' + val.toString().split('.')[1];
  }

  // return result with - sign if negative
  return sign < 0 ? '-' + num : num;
}
// decimal number
let num1 = 77799;
console.log(commaSeparateNumber(num1));

// decimal number
let num2 = -72364769.1234;
console.log(commaSeparateNumber(num2));

JavaScript Number Format Currency

JavaScript has a built-in method that can be used to format numbers for currency, it is Intl.NumberFormat().

It is part of the Intl (international) object. The Intl.NumberFormat() method creates an object that is language sensitive and can be used to format numbers for currency.

It accepts 2 optional arguments: locale (en-US, hi-IN, etc) and options({style, currency}).

Example

const number = 76346.45;

// United state $
let num = new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD' }).format(number);
console.log(num);
// Indian rupee ₹
num = new Intl.NumberFormat('hi-IN', { style: 'currency', currency: 'INR' }).format(number);
console.log(num);

The same is also achievable using the toLocaleString() method.

Example

var number = 76346.45;

// request a currency format
var num = number.toLocaleString('hi-IN', { style: 'currency', currency: 'INR' })
console.log(num);

// United state $
num = number.toLocaleString('en-US', { style: 'currency', currency: 'USD' })
console.log(num);

Conclusion

JavaScript numbers can be formatted in different ways like commas, currency, etc. You can use the toFixed() method to format the number with decimal points, and the toLocaleString() method to format the number with commas and Intl.NumberFormat() method to format the number with currency.

You can also create your own custom function to format the number. This article covers all types of number conversion.