I am trying to retain leading zeroes in an integer/number within JavaScript.

In this example I have an "ItemName" key which has either a string or an integer as its value.

I only want to have integers to be the value, but when I try converting any string value to a number, it will remove the leading zeroes.

I need to retain the zeroes so that the data sent will reliably be 6 digits, where in the example it would only be 4 digits.

The value is intended to be an identifier for a given Item.

{"Item": [{"ItemName":"007730","BusinessUnit":1}] } 
{"Item": [{"ItemName":917730,"BusinessUnit":1}] }

This is for my work and we use ES6, but if there's an option outside of that, I'm certainly open to it. Thanks in advance!

I am trying to retain leading zeroes in an integer/number within JavaScript.

In this example I have an "ItemName" key which has either a string or an integer as its value.

I only want to have integers to be the value, but when I try converting any string value to a number, it will remove the leading zeroes.

I need to retain the zeroes so that the data sent will reliably be 6 digits, where in the example it would only be 4 digits.

The value is intended to be an identifier for a given Item.

{"Item": [{"ItemName":"007730","BusinessUnit":1}] } 
{"Item": [{"ItemName":917730,"BusinessUnit":1}] }

This is for my work and we use ES6, but if there's an option outside of that, I'm certainly open to it. Thanks in advance!

• javascript
• number-formatting
• identifier
• leading-zero

Share Improve this question Follow asked Nov 26, 2021 at 16:17 Voltaire22Voltaire22 2311 silver badge33 bronze badges 4

• 2 You can only do this as a string. So convert the Number type to a string and pad front with zeros. When you convert this number back to an integer you'll have to remove the leading zeros. Mathematically, leading zeros have no meaning on an integer. They might to humans, hence strings show zeros, but mathematical representations of numeric things won't. – Randy Casburn Commented Nov 26, 2021 at 16:27
• 1 In addition to what was said/explained by Randy Casburn ... String.prototype.padStart – Peter Seliger Commented Nov 26, 2021 at 16:39
• 1 btw ... ItemName already strongly hints a string. Anyway it should never get assigned a number value like 917730. – Peter Seliger Commented Nov 26, 2021 at 17:01
• 2 Thanks for the response! I guess we'll just have to make sure they're all strings across our systems. – Voltaire22 Commented Nov 26, 2021 at 17:04

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 6

You can't have a number with leading zeroes in Javascript, because, as Randy Casburn said, they don't have any value. You have to convert it to a string and use String.padStart() to pad the string with zeroes. parseInt will work with leading zeroes. For example:

(294).toString().padStart(6, "0") --> "000294"


parseInt("000294") --> 294

This can be done with Intl.NumberFormat like this:

const num = 7730;
const formattedNum = new Intl.NumberFormat('en', { minimumIntegerDigits: 6, useGrouping: false }).format(num);
console.log(formattedNum);