Convert values to boolean in JS

boolean.js

// In JS `!!` can be used to convert any value to a boolean
// Similar to using the Boolean() function

(function() {
  var foo = 'foo';
  console.log(typeof foo);

  var bool = !!foo;
  console.log(typeof bool);
  console.log(bool);
})()

// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean
// http://brianflove.com/2014/09/02/whats-the-double-exclamation-mark-for-in-javascript/
// https://stackoverflow.com/questions/784929/what-is-the-not-not-operator-in-javascript#answer-15035152
// https://stackoverflow.com/questions/29312123/how-does-the-double-exclamation-work-in-javascript#answer-29312197
// https://medium.com/@pddivine/javascript-bang-bang-i-shot-you-down-use-of-double-bangs-in-javascript-7c9d94446054