What types of recognition are available in JS

2. 1. Use typeof.
4. Direct use without encapsulation.
6. Flag type can be recognized (except NULL)
8. Specific object types are not recognized
10. typeof(1); "Number"
12. typeof(""); "String"
14. typeof([]); "Object"
16. typeof({}); "Object"
18. typeof(null); "Object"
20. typeof(undefined); "Undefined"
24. 2.instanceof
26. No need to use encapsulation
28. Ability to distinguish built-in object types
30. [] instanceof Array; True
32. /\d/ instanceof RegExp; True
34. Primitive types cannot be distinguished
36. 1 instanceof number ; False
38. "Xiaohong" instanceof String; False
40. Ability to discriminate between custom types
42. function point (x, y) {
44. this. x = x;
46. this. y = y;
48. }
50. var c = new Point (2,3);
52. C instanceof Point ; True
56. 3.object.prototype.tostring.call () method.
58. Object.prototype.toString.call (21); //"[Object number]"
60. Object.prototype.toString.call ([]); //"[Object Array]"
62. For ease of use, the function is typically encapsulated as follows
64. function Typeprototype (obj) {
66. return Object.prototype.toString.call (obj). Slice (8,-1);
68. }
70. Typeprototype ("Guo"); "String"
72. Typeprototype ({}); //"Object"
74. Can recognize standard types, and built-in object types
76. Custom type not recognized
82. 4.constuructor points to the constructor that constructs the object itself:
84. Can distinguish the original type
86. "Guo". constructor = = = String; True
88. (1). constructor = = = number; //true
90. True. Constructor = = = Boolean; True
92. ({}). constructor = = = Object; //true
94. Can discriminate built-in object type
96. New Date (). constructor = = = Date; True
98. [].constructor = = = Array; //true
102. Custom types are recognized
104. function people (x, y) {
106. this. x = x;
108. this. y = y;
110. }
112. var c = new people (2,3);
114. C.constructor===people; //true
116. The function is encapsulated as follows
118. function getconstructorname (obj) {
120. return obj && obj.constructor && obj.constructor.toString (). Match (/function\s* ([^ (] *)/) [1];
122. }
124. Using && short-circuit characteristics
126. 1 obj//can be returned directly if the entry parameter is undefined and null because it has no constructor value
128. 2 obj.constructor//Ensure that the following expression is executed correctly
130. 3 obj.constructor.toString ()//convert constructor to string "function number () {}"
132. 4. Match (/function\s* ([^ (]*)/) [1]//Gets the value of the type in the constructor string "number"
134. Getconstructorname (new Date ()); "Date"
136. Getconstructorname (null); Null
138. Getconstructorname (12); //"number"

What types of recognition are available in JS