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# How to Output Numbers With Leading Zeros in JavaScript?

Sometimes, we want to output numbers with leading zeroes in our JavaScript programs.

The JavaScript string’s `padStart` method lets us add characters we want to a string until it reaches a given length.

For instance, we can write:

``````const padded = (123).toString().padStart(5, '0')
``````

We call `toString` on the number to convert it to a string.

Then we call `padStart` with 5 to pad the string to length 5.

And we pass in `'0'` to pad the number with leading 0’s.

Therefore, `padded` is `'00123'` .

### Write Our Own Code

We can also write our own code to pad a number string with leading zeroes.

For instance, we can write:

``````const zeroPad = (num, places) => {
const numZeroes = places - num.toString().length + 1;
if (numZeroes > 0) {
return Array(+numZeroes).join("0") + num;
}
return num
}

``````

We create the `zeroPad` function that takes the `num` and `places` parameters.

`num` has the number we want to pad with leading zeroes.

`places` is the number of decimal places that we want to pad to.

In the function, we compute the `numZeroes` variable, which is the number of leading zeroes we want to add to make the string the length set by `places` .

We compute that by substracting `places` with `num.toString().length` plus 1.

This subtracts the final number of places with the length of the number string plus 1.

We add 1 so that we create the correct sized array since we want to add zeroes in between the array entries with `join` .

Then if `numZeroes` is bigger than 0, we return a string with leading zeroes by creating an array, then calling `join` with 0 to create the zero string, and then concatenating that with the `num` value.

Otherwise, we return `num` itself.

So the console log should log:

``````05
0005
000005
``````

### Conclusion

We can pad our JavaScript nuinmber strings with leading zeroes with the `padStart` method or write our own code to do so.

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