1 var isString1 = function (obj){
 2    return Object.prototype.toString.call(obj)==="[object String]";
 3 };
 4 
 5 
 6 var isString2 = function(obj){
 7     return (typeof obj==="string")
 8 };
 9 
10 
11 var isString3 = function (obj) {
12     return ("" + obj) === obj;
13 };

 1 var isArray1 = function(obj){
 2     return Object.prototype.toString.call(obj)==="[object Array]"
 3 };
 4 
 5 var isArray2 = function(obj){
 6     return obj instanceof Array;
 7 };
 8 
 9 var isArray3 = function(obj){
10     return Array.isArray(obj); //需要浏览器支持
11 };

 1  var toString = Object.prototype.toString;
 2 
 3 
 4    //判读一个对象是一个对象
 5   _.isObject = function(obj) {
 6     var type = typeof obj;
 7     return type === ‘function‘ || type === ‘object‘ && !!obj;
 8   };
 9 

10   // isArguments, isFunction, isString, isNumber, isDate, isRegExp, isError.
11   _.each([‘Arguments‘, ‘Function‘, ‘String‘, ‘Number‘, ‘Date‘, ‘RegExp‘, ‘Error‘], function(name) {
12     _[‘is‘ + name] = function(obj) {
13       return toString.call(obj) === ‘[object ‘ + name + ‘]‘;
14     };
15   });