# How To Add Leading & Trailing Zeroes To Numbers In Javascript

Welcome to a short tutorial on how to add leading and trailing zeroes to numbers in Javascript. So you have some numbers that require padding of zeroes?

The easy way to add leading or trailing zeroes in Javascript is to:

1. Concatenate the number with a string of zeroes.
• `var num = "000" + 123;`
• `var num = 123.45 + "000";`
2. Or use the string pad functions.
• `var num = "123".padStart(5, 0);`
• `var num = "123.45".padEnd(8, 0);`

That covers the basics, but let us walk through a few more examples – Read on!

ⓘ I have included a zip file with all the example source code at the start of this tutorial, so you don’t have to copy-paste everything… Or if you just want to dive straight in.

## QUICK SLIDES Firstly, here is the download link to the example code as promised.

### QUICK NOTES

If you spot a bug, feel free to comment below. I try to answer short questions too, but it is one person versus the entire world… If you need answers urgently, please check out my list of websites to get help with programming.

Click here to download the source code, I have released it under the MIT license, so feel free to build on top of it or use it in your own project.

## PAD WITH ZEROES All right, let us now go into the examples of padding a number with leading and trailing zeroes.

### EXAMPLE 1) EASY LEADING & TRAILING ZEROES

1-easy.html
``````// (A) THE NUMBERS
var numA = 123;
var numB = 123.45;

// (B) STRING CONCAT
console.log("000" + numA);
console.log(numB + "000");

// (C) PAD STRING

As in the introduction above, the easiest way to pad a number with zeroes is to either –

• Concatenate with a string of zeroes.
• Or convert the number to string, then use the pad string functions.

### EXAMPLE 2) MANUAL PAD LEADING & TRAILING ZEROES

``````// (A) PAD WITH ZEROES
//   NUM : THE ORIGINAL NUMBER
//   LEAD : TOTAL NUMBER OF DIGITALS ALLOWED (WHOLE NUMBERS)
//   TRAIL : TOTAL NUMBER OF DIGITALS ALLOWED (DECIMAL NUMBERS)
// (A1) CONVERT NUMBER TO STRING
var cString = num.toString();

// (A2) GET NUMBER OF DIGITS
var cWhole, cDec, cCheck = cString.indexOf(".");

// NO DECIMAL PLACES, A WHOLE NUMBER
if (cCheck == -1) {
cWhole = cString.length;
cDec = 0;
cString += ".";
}
// IS A DECIMAL NUMBER
else {
cWhole = cCheck;
cDec = cString.substr(cCheck+1).length;
}

if (cWhole < lead) {
for (let i=cWhole; i<lead; i++) { cString = "0" + cString; }
}

// (A4) PAD WITH TRAILING ZEROES
if (cDec < trail) {
for (let i=cDec; i<trail; i++) { cString += "0"; }
}

return cString;
}

// (B) TEST
// (B1) WHOLE NUMBER
var first = padZero(123, 5, 3);
console.log(first); // 00123.000

// (B2) DECIMAL
var second = padZero(123.45, 5, 3);
console.log(second); // 00123.450``````

Once upon a time in the Dark Ages of the Internet, this is how we pad a number with zeroes… Essentially:

• (A1) Convert the number into a string first.
• (A2) Split the number into “whole numbers” and “decimals”.
• (A3 & A4) Add the leading and/or trailing zeroes as required.

### EXTRA) REMOVE ZEROES

3-remove-zero.js
``````// (A) PARSE FLOAT & INT
console.log(parseFloat("0123.4500")); // 123.45
console.log(parseInt("0123.4500")); //123

// (B) USING REGULAR EXPRESSION
function removeZero (num) {
return num.replace(/^0+(?!\.|\$)/, "");
}
console.log(removeZero("000.00")); // 0.0
console.log(removeZero("00000")); // 0
console.log(removeZero("012.30")); // 12.30``````

Finally, a small extra to do the opposite of removing zeroes –  Simply use `parseFloat()` or `parseInt()` and that’s it. But if you want a “smarter remove zero” – Using regular expressions is the only way to go.

## USEFUL BITS & LINKS That’s all for this tutorial, and here is a small section on some extras and links that may be useful to you.

### SUMMARY

 Function Description Reference `.toString()` One of the most important functions to convert number or decimal to a string – Pad with zeroes, add commas or period. Click Here `.indexOf("CHARACTER")` Finds the position of the given character in a string. Click Here `STRING.padStart(LENGTH, WITH)` Pad the start of string with the given character. Click Here `STRING.padEnd(LENGTH, WITH)` Pad the end of string with the given character. Click Here `parseInt(STRING)` Parse a string into an integer. Click Here `parseFloat(STRING)` Parse a string into a float. Click Here

### INFOGRAPHIC CHEAT SHEET 