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Boolean

Another important data type next to String and Number is Boolean. It has only two possible values: true and false. You can calculate with Boolean values similar to numbers. JavaScript has three Boolean operators: && (and), || (or) and ! (not). && links two Boolean values. If both values are true, the result is true. In all other cases it is false. With || the result is true, if at least one of the two input values is true. If both input values are false, the result is false. ! is applied to a single Boolean value and inverts this value: !true is false and !false is true.
let x1 = true && false;
let x2 = !x1;
let x3 = x1 || x2;
x1 is false, x2 is true and x3 is true.

Exercise

Write a function nand that takes two Boolean values. If both values are true, the result should be false. In the other cases the return should be true.

I.e.: The call nand(true, true) should return false. The calls nand(true, false), nand(false, true) and nand(false, false) should return true.
function nand(a, b) {
  let and = a && b;
  ...
}
function nand(a, b) {
  let and = a && b;
  return !and;
}

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