/**
  * param：o表示檢測的值
  * return：返回字符串"undefined"、"number"、"boolean"、"string"、"function"、"regexp"、"array"、"date"、"error"、"object"或"null"
  */
function typeOf(o){
    var _toString = Object.prototype.toString;  //獲取對象的toString()方法引用
    //列舉基本數據類型和內置對象類型，你還可以進一步補充該數組的檢測數據類型范圍
    var _type ={
        "undefined" : "undefined",
        "number" : "number",
        "boolean" : "boolean",
        "string" : "string",
        "[object Function]" : "function",
        "[object RegExp]" : "regexp",
        "[object Array]" : "array",
        "[object Date]" : "date",
        "[object Error]" : "error"
    }
    return _type[typeof o] || _type[_toString.call(o)] || (o ? "object" : "null"); //通過把值轉換為字符串，然后匹配返回字符串中是否包含特定字符進行檢測
}
//應用示例：
var a = Math.abs;
alert(typeOf(a));  //返回字符串"function"