# js add zeros before number

## How to Add Zeros Before a Number in JavaScript

If you want to add zeros before a number in JavaScript, you can use the `padStart()`

method. This method adds a specified number of characters at the beginning of a string.

### Syntax:

`string.padStart(targetLength [, padString])`

`targetLength`

: The length of the resulting string once the padding is applied. If this value is less than the original string length, no padding will be added.`padString`

(optional): The string to use for padding. The default is whitespace.

Here's an example:

```
let num = '5';
num = num.padStart(3, '0'); // Output: '005'
```

In this example, we have a number `5`

and we want to add zeros before it to make it a three-digit number. We use the `padStart()`

method and pass the target length as 3 and the pad string as `'0'`

. The resulting string is `'005'`

.

If you have a number that is already a string, you can convert it to a number and then use the `toString()`

method to convert it back to a string with padded zeros. Here's an example:

```
let num = '5';
let paddedNum = (+num).toString().padStart(3, '0'); // Output: '005'
```

In this example, we convert the string `'5'`

to a number using the `+`

operator. Then, we convert the number back to a string using the `toString()`

method and apply the `padStart()`

method to add zeros before the number.

Another way to add zeros before a number in JavaScript is to use the `repeat()`

method. This method creates a new string by repeating a specified string a certain number of times. Here's an example:

```
let num = '5';
let zeroString = '0'.repeat(3 - num.length);
let paddedNum = zeroString + num; // Output: '005'
```

In this example, we first calculate the number of zeros we need to add by subtracting the length of the number from the target length. We use the `repeat()`

method to create a string of zeros with the calculated length. Then, we concatenate the zero string and the original number to get the padded number.

### Conclusion:

Adding zeros before a number in JavaScript is easy using the `padStart()`

method. You can also use other methods like `toString()`

and `repeat()`

to achieve the same result.