js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;
    }

    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