--description--

Given a string, determine if all the characters in the string are unique.

• Uppercase and lowercase letters should be considered different characters.

--hints--

allUnique("abc") should return true.

assert.isTrue(allUnique("abc"));

allUnique("aA") should return true.

assert.isTrue(allUnique("aA"));

allUnique("QwErTy123!@") should return true.

assert.isTrue(allUnique("QwErTy123!@"));

allUnique("~!@#$%^&*()_+") should return true.

assert.isTrue(allUnique("~!@#$%^&*()_+"));

allUnique("hello") should return false.

assert.isFalse(allUnique("hello"));

allUnique("freeCodeCamp") should return false.

assert.isFalse(allUnique("freeCodeCamp"));

allUnique("!@#*$%^&*()aA") should return false.

assert.isFalse(allUnique("!@#*$%^&*()aA"));

--seed--

--seed-contents--

function allUnique(str) {

  return str;
}

--solutions--

function allUnique(str) {
  let seen = '';
  for (let char of str) {
    if (seen.includes(char)) {
      return false;
    }
    seen += char;
  }
  return true;
}