aurelius - 1 year ago 125

Javascript Question

I have this regex which validates if a string is a decimal number.

Also this checks if it has at most 9 decimals after ".".

`^[-]?[0-9]+([\.][0-9]{0,9})?$`

I need to add another check, which limits the total number of digits.

Mention: I need the total number of digits to be less then 38, including the decimal after the point, thus I cannot add the range just to decimals before the point.

valid ex:

`-12345678901234567890123456789.123456789`

123456789012345678901234567890.1

-1.123456789

Answer Source

You can use regex with positive look ahead assertion `/^-?(?=[.\d]{0,39}$)\d{0,38}(\.\d{1,9})?$/`

```
$('input').on('input', function() {
$(this).css('color', /^-?(?=[.\d]{0,39}$)\d{0,38}(\.\d{1,9})?$/.test(this.value) ? 'green' : 'red');
})
```

```
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<input>
```