var num=10; console.log(num+10);
//沙箱---小环境 (function () { var num = 10; console.log(num); })();
//沙箱---小环境 (function () { var num = 20; console.log(num + 10); }());
里外相互不影响
var num = 100; (function () { var num = 10; console.log(num);//10 }()); console.log(num);//100
原文:https://www.cnblogs.com/jane-panyiyun/p/12175418.html