实现一个函数判断数据类型
function getType(obj){
if(obj === null) return String(obj)
return typeof obj=== 'object' ?
Object.prototype.toString.call(obj).replace('[object ','').replace(']','').toLowerCase()
: typeof obj;
}
// 调用
console.log(getType(null)); // -> null
console.log(getType(undefined)); // -> undefined
console.log(getType({})); // -> object
console.log(getType([])); // -> array
console.log(getType(123)); // -> number
console.log(getType(true)); // -> boolean
console.log(getType('123')); // -> string
console.log(getType(/123/)); // -> regexp
console.log(getType(new Date())); // -> date
