I am trying to replace the text of an input. If I enter this value (11111111), the output format should be (1,111,111-1). I have no idea how to do this using js vanilla. I am trying to use regex and replace but I'm very confused.
let regExp = /^[1-9].\d{3}.\d{3}-\d{1}$/g;
let newInput = input.replace(regExp, '$1,');
console.log( newInput);
The regex is for the match, which must match the input string. Use the replacement pattern to reformat the output:
let input = '11111111'
let regExp = /^(\d)(\d{3})(\d{3})(\d)$/g;
let newInput = input.replace(regExp, '$1,$2,$3-$4');
console.log( newInput);