String Anagram

// Take input two strings from user
var userFirstInput = prompt('Enter a First String...');
var userSecondInput = prompt('Enter a Second String...');

// Displaying strings which is entered by user
document.write('Entered string by you = <strong>' + userFirstInput + '</strong><br>');
document.write('Entered string by you = <strong>' + userSecondInput + '</strong><br><br>');

// Check whether given strings are Anagram or not
var firstSplittedArray = userFirstInput.toLowerCase().split('').sort();
var secondSplittedArray = userSecondInput.toLowerCase().split('').sort();

var notAlphabetRegEx = /[^a-z]+/;

while (notAlphabetRegEx.test(firstSplittedArray[0])) {
    firstSplittedArray.splice(0, 1);
}
while (notAlphabetRegEx.test(secondSplittedArray[0])) {
    secondSplittedArray.splice(0, 1);
}

var bool = false;
if (firstSplittedArray.length === secondSplittedArray.length) {
    for (i in firstSplittedArray) {
        bool = firstSplittedArray[i] === secondSplittedArray[i];
        if (bool === false) {
            break;
        }
    }
}

// Displaying strings are Anagram or not
if (bool) {
    document.write('String <strong>' + userFirstInput + '</strong> and String <strong>' + userSecondInput + '</strong>' + ' are Anagram of each and other.');
} else {
    document.write('String <strong>' + userFirstInput + '</strong> and String <strong>' + userSecondInput + '</strong>' + ' are not Anagram of each and other.');
}