Why let is the new var?

let.js

// Exists since ES6
let isTheNewVar = '☝️😙';

function why() {

  let result = 'Well, actually…';

  if (!window.isTheNewVar) {
    let isTheNewVar = 'BECAUSE IT CANNOT CREATE "GLOBAL" PROPERTIES! 🎉';
    let result = 'ALSO BECAUSE IT IS BLOCK-SCOPED! 😎';
    setTimeout(() => { console.log(`${isTheNewVar} ${result}`) }, 0);
  }

  console.log(`Why?!`);
  console.log(result);
}

/* guess */ why() /* ? */

setTimeout(() => { console.log(`OH, AND IT CANNOT BE RE-DECLARED (you'll see in 3,2,1… 💥)`) }, 0);
setTimeout(() => {
  let uh = '👀';
  let uh = '👅';
}, 3000);

setTimeout(() => {
  console.log(`Bonus: NO HOISTING ANYMORE! 😱 Wait… now there's a thing called "Temporal Dead Zone" 😬`);
  try {
    console.log(`TDZ: ${TDZ}`);
    let TDZ = '💀';
  } catch(err) {
    console.error(`Ups! ${err}`);
    // Mmmmh-ake sense! BUT REMEMBER... IT'S TEMPORAL, NOT SPATIAL:
    function WAT() {
      console.log(`Messing with TDZ: ${TDZ}`);
    }

    let TDZ = '💀';

    WAT();  
  }
}, 6000);