1. 那个是正确的

    1.for (let index = 0; index < 12; index++) {};console.log(index);//谬误2.const a = 12;a = 13;console.log(a);//谬误3.const G = {a:3};console.log(G.a);G.b=12;console.log(G.b);// 3,124.let [head,...tail] = [1,2,3,4];console.log(tail)// [2,3,4]
  2. 请问输入的是 // GoodByeJack

    var name = 'world';(function () { var name; if (typeof name === "undefined") {     name = 'Jack';     console.log('GoodBye'+name) } else {     console.log('hello'+name) }})();