Input:
const inputString1 = "4rontender";
const inputString2 = "coder";
Output:
checkUniqueChars(inputString1); // "4rontender": false
checkUniqueChars(inputString2); // "coder": true
Input:
const inputString1 = "abcdef";
const inputString2 = "123456";
const inputString3 = "abcABC";
const inputString4 = "abcaef";
Output:
isUnique(inputString1); // "abcdef", true
isUnique(inputString2); // "123456", true
isUnique(inputString3); // "abcABC", true
isUnique(inputString4); // "abcaef", false