var y = (x) => {return x + 1} var y = function(x) { return x + 1; } var z = (x, y) => ({ x: x, y: y }) var z = function(x, y) { return { x: x, y: y }; } ES6 ES5
var vs let (function() { if (true) { let y = “value”; } console.log(y) // ERROR!! }()); (function() { console.log(y) // “undefined” if (true) { var y = “value”; } console.log(y) // “value” }());
var array = [“a”, “b”, “c”]; ! for (let [index, el] of array.entries()) { console.log(index, el); // 0 “a” // 1 “b” // 2 “c” } ! for (let index of array.keys()) { console.log(index); } ! for (let el of array.values()) { console.log(el); } !