Regular Expression to reformat a US phone number in Javascript

Question

I\'m looking to reformat (replace, not validate - there are many references for validating) a phone number for display in Javascript. Here\'s an example of some of the data:

Answer 1

Almost all of these have issues when the user tries to backspace over the delimiters, particularly from the middle of the string.

Here's a jquery solution that handles that, and also makes sure the cursor stays in the right place as you edit:

//format text input as phone number (nnn) nnn-nnnn
$('.myPhoneField').on('input', function (e){
    var $phoneField = e.target;
    var cursorPosition = $phoneField.selectionStart;
    var numericString = $phoneField.value.replace(/\D/g, '').substring(0, 10);

    // let user backspace over the '-'
    if (cursorPosition === 9 && numericString.length > 6) return;

    // let user backspace over the ') '
    if (cursorPosition === 5 && numericString.length > 3) return;
    if (cursorPosition === 4 && numericString.length > 3) return;

    var match = numericString.match(/^(\d{1,3})(\d{0,3})(\d{0,4})$/);
    if (match) {
        var newVal = '(' + match[1];
        newVal += match[2] ? ') ' + match[2] : '';
        newVal += match[3] ? '-' + match[3] : '';

        // to help us put the cursor back in the right place
        var delta = newVal.length - Math.min($phoneField.value.length, 14);      
        $phoneField.value = newVal;
        $phoneField.selectionEnd = cursorPosition + delta;
    } else {
        $phoneField.value = '';        
    }
})