var obj = {a:1,age:18,birthday:'2-14'}; function demo(obj){ var a = []; //这句代码什么鬼? for(a[a.length] in obj); return a; }
function demo(obj){ var a = []; //遍历对象的可枚举属性,比如 a=[1]是a['0']=1 for(a[a.length] in obj); //数组也是对象 return a; }
a[a.length] => a['0']
把obj的元素追加到数组a中
for(a[a.length] in obj);循环遍历obj中的元素放在a中初始a.length = 0第一次遍历:a[0] = 'a' 后a.length = 1第二次遍历:a[1] = 'age' 后a.length = 2第三次遍历:a[2] = 'birthday' 最后a=['a', 'age','birthday']一个数组返回
for(a[a.length] in obj);
a.length = 0
a[0] = 'a'
a[1] = 'age'
a[2] = 'birthday'
a=['a', 'age','birthday']