JavaScript 判断一个对象的数据类型。

1、isString

 var isString1 = function (obj){
    return Object.prototype.toString.call(obj)==="[object String]";
 };

 var isString2 = function(obj){
     return (typeof obj==="string")
 };

 var isString3 = function (obj) {
     return ("" + obj) === obj;
 };

2、isArray

 var isArray1 = function(obj){
     return Object.prototype.toString.call(obj)==="[object Array]"
 };

 var isArray2 = function(obj){
     return obj instanceof Array;
 };

 var isArray3 = function(obj){
     return Array.isArray(obj); //需要浏览器支持
 };

3、其他

  var toString = Object.prototype.toString;

    //判读一个对象是一个对象
   _.isObject = function(obj) {
     var type = typeof obj;
     return type === 'function' || type === 'object' && !!obj;
   };
 
   // isArguments, isFunction, isString, isNumber, isDate, isRegExp, isError.
   _.each(['Arguments', 'Function', 'String', 'Number', 'Date', 'RegExp', 'Error'], function(name) {
     _['is' + name] = function(obj) {
       return toString.call(obj) === '[object ' + name + ']';
     };
   });