Javascript Interview Question String Cipher String

Introduction

Given inputs a string, and a number shift, return a new encrypted string by shifting each letter of the sting by shift number of places

Example: 

caesarCipher('RETURN TO ROME', 3) should return 'UHWXUA WR URPH'

To reduce complexity of the problem, you may assume every character in the string will be uppercase. 

function caesarCipher (string, shift) {
}
/*  Do not edit below this line */

var line = '****************************************************************';
var passed = 0;/* w ww.j a va 2  s. c  o  m*/
var failed = 0;

console.log(line);
console.log('caesarCipher UNIT TESTS');
console.log(line);

if (caesarCipher('RETURN TO ROME', 3) === 'UHWXUQ WR URPH') {
    console.log("Test 1 pass, caesarCipher('RETURN TO ROME', 3) returns 'UHWXUQ WR URPH'");
    passed += 1;
} else {
    console.log("Test 1 failed, caesarCipher('RETURN TO ROME', 3) should return 'UHWXUQ WR URPH'");
    failed += 1;
}

if (caesarCipher('XYZ', 3) === 'ABC') {
    console.log("Test 2 pass, caesarCipher('XYZ', 3) returns 'ABC'");
    passed += 1;
} else {
    console.log("Test 2 failed, caesarCipher('XYZ', 3) should return 'ABC'");
    failed += 1;
}

if (caesarCipher('ABC', -3) === 'XYZ') {
    console.log("Test 3 pass, caesarCipher('ABC', -3) returns 'XYZ'");
    passed += 1;
} else {
    console.log("Test 3 failed, caesarCipher('ABC', -3) should return 'XYZ'");
    failed += 1;
}

console.log(line);
console.log('TOTAL TESTS PASSED: ' + passed );
console.log('TOTAL TESTS FAILED: ' + failed );
console.log(line);




function caesarCipher (string, shift) {
    var alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
    var encryptedString = '';
    var char = '';
    var charPosition;
    var encryptedPosition;

    for (var i = 0; i < string.length; i += 1) {
        // We first check if the charactre we are on is a letter
        char = string[i];
        charPosition = alphabet.indexOf(char);
        
        // If it is a letter, shift the character's position in the alphabet by shift number
        // We then mod it by 26 which is the number of letters in the alphabet to catch overflow situations
        if (charPosition > -1) {
            // 26 is added to allow shift in the opposit direction when shift is a negative number
            encryptedPosition = (charPosition + shift + 26) % 26;
            encryptedString = encryptedString + alphabet[encryptedPosition];
        }else{
            encryptedString = encryptedString + char;
        }
    }

    return encryptedString;
}






/*  Do not edit below this line */

var line = '****************************************************************';
var passed = 0;
var failed = 0;

console.log(line);
console.log('caesarCipher UNIT TESTS');
console.log(line);

if (caesarCipher('RETURN TO ROME', 3) === 'UHWXUQ WR URPH') {
    console.log("Test 1 pass, caesarCipher('RETURN TO ROME', 3) returns 'UHWXUQ WR URPH'");
    passed += 1;
} else {
    console.log("Test 1 failed, caesarCipher('RETURN TO ROME', 3) should return 'UHWXUQ WR URPH'");
    failed += 1;
}

if (caesarCipher('XYZ', 3) === 'ABC') {
    console.log("Test 2 pass, caesarCipher('XYZ', 3) returns 'ABC'");
    passed += 1;
} else {
    console.log("Test 2 failed, caesarCipher('XYZ', 3) should return 'ABC'");
    failed += 1;
}

if (caesarCipher('ABC', -3) === 'XYZ') {
    console.log("Test 3 pass, caesarCipher('ABC', -3) returns 'XYZ'");
    passed += 1;
} else {
    console.log("Test 3 failed, caesarCipher('ABC', -3) should return 'XYZ'");
    failed += 1;
}

console.log(line);
console.log('TOTAL TESTS PASSED: ' + passed );
console.log('TOTAL TESTS FAILED: ' + failed );
console.log(line);



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