JS高級---沙箱

沙箱

var num=10;
console.log(num+10);

    //沙箱---小環境
    (function () {
      var num = 10;
      console.log(num);
    })();

    //沙箱---小環境
    (function () {
      var num = 20;
      console.log(num + 10);
    }());

裡外相互不影響

    var num = 100;
    (function () {
      var num = 10;
      console.log(num);//10
    }());


    console.log(num);//100