Other possible solution for challenge 02/09 format phone number using regex

[tre-tom]

There is a solution possible with format phone number using regexes and replacing groups. So whatever you put inside brackets, you can then reference in the replace clause using $1 $2 and so on.

Here is the code:

const formatPhoneNumber = (numbers) => numbers
    .reduce((output, number) => output + number, '')
    .replace(/([0-9]{3})([0-9]{3})([0-9]{4})/, '($1) $2-$3')

So I am first converting the numbers array into string using reduce.
Then I am creating regex groups in the left side of replace statement:

• ([0-9]{3}) means first 3 digits will be accessible via $1
• ([0-9]{3}) means next 3 digits will be accessible via $2
• ([0-9]{3}) means last 4 digits will be accessible via $3

Then you can reference it in the right side of replace statement using ($1) $2-$3.