js判断字符串、数组、对象的数据类型

 1 var str1=new String('str1');
 2 var str2='str2';
 3 console.log(typeof str1);// 
 4 console.log(typeof str2);//string
 5 console.log(str1 instanceof String);//true
 6 console.log(str2 instanceof String);//false
 7 console.log(str1.constructor==String);//true
 8 console.log(str2.constructor==String);//true
 9 
10 var a = ['hello','world'];
11 console.log(typeof a);// 
12 console.log(a.toString());//hello,world
13 console.log( .prototype.toString.call(a));//[  Array]
14 console.log(Array.prototype.isPrototypeOf(a));//true
15 console.log(Array.isArray(a));//true
16 console.log(a instanceof Array);//true
17 console.log(a instanceof  );//true
18 console.log(a.constructor==Array);//true
19 console.log(a.constructor== );//false
20 
21 var b = {'hello':'world'};
22 console.log(typeof b);// 
23 console.log(b.toString());//[   ]
24 console.log( .prototype.toString.call(b));//[   ]
25 console.log( .prototype.isPrototypeOf(b));//true
26 console.log(b instanceof  );//true
27 console.log(b.constructor== );//true