jsES6新特性总结const 与 let 变量使用var带来的麻烦:function getClothing(isCold) { if (isCold) { var freezing = 'Grab a jacket!'; } else { var hot = 'It's a shorts kind of day.'; console.log(freezing); }}运行getClothing(false)后输出的是undefined,这是因为执行function函数