I'm trying to auto format an input on HTML with javascript, and it is almost done, i need the format to be xxx-xxx-xxxx but and I have this code

this.value = this.value.replace(/(\d{3})\-?/g,'$1-');

as youy can see it will just auto format xxx-xxx-xxx but I need to be 4 digits at the end

any sugestions?

I'm trying to auto format an input on HTML with javascript, and it is almost done, i need the format to be xxx-xxx-xxxx but and I have this code

this.value = this.value.replace(/(\d{3})\-?/g,'$1-');

as youy can see it will just auto format xxx-xxx-xxx but I need to be 4 digits at the end

any sugestions?

• javascript
• jquery
• html
• regex

Share Improve this question Follow edited Apr 9, 2014 at 20:05 kei 20.5k22 gold badges3737 silver badges6464 bronze badges asked Apr 9, 2014 at 19:57 user3516479user3516479 1144 bronze badges

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4 Answers 4

Sorted by: Reset to default 4

Try this regexp:

'1234567890'.replace(/(\d{3}(?!\d?$))\-?/g, '$1-'); // 123-456-7890

The part (?!\d?$) is a negative lookahead. It allows regular expression to match three digits only if they are not followed by another number (4th) (but not necessarily ?) at the end of the string $.

So it will not match 789 group because it's followed by 0$.

Or simply : .replace(/(\d{3})(\d{3})(\d{4})\-?/g,'$1-$2-$3');

Sample code to help you out:

var phone = '(555) 666-7777';

// First clean your input
phone = phone.replace(/[^\d]/g, '');
// Check the length of the phone
if(phone.length == 10){
    // Now we can format the phone
    phone = phone.substring(0,3)+'-'+phone.substring(3,6)+'-'+phone.substring(6, 10);
    // Optionally
    //phone = phone.replace(/(\d{3})(\d{3})/, '$1-$2-');
}
else {
    // whatever you want to tell the user
}

there seems to be a bug in the "replace" regex's above. enter a 10 digit number and you see it formatted correctly (e.g. "(123) 456-7890"). Then, select the contents of the field (double or triple click it) and overtype the value. You'll see the first two digits get transposed. So if you enter 1 2 3, you'll see 2 1 3...