Javascript determines whether a specific class of an object is reprinted

We all know that Javascript typeof can obtain the type of the variable, but typeof has only six return values: "number," "string," "boolean," "object," "function, "and" undefined."

In fact, Javascript still has many special categories, such as Array and Date. Why can't they be returned in typeof?
Originally, Javascript classifies Array Date objects into Object classes. We can only use instanceof to determine the exact object category.

Here is a simple example to illustrate the usage of instanceof.
Copy codeThe Code is as follows:
Function objTest (obj ){
Var I, t, s = ""; // create a variable.
T = new Array (); // create an Array.
T ["Date"] = Date; // fill in the array.
T ["Object"] = Object;
T ["Array"] = Array;
For (I in t)
{
If (obj instanceof t [I]) // check the obj class.
{
S + = "obj is an instance of" + I + "\ n ";
}
Else
{
S + = "obj is not an instance of" + I + "\ n ";
}
}
Return (s); // return a string.
}

Var obj = new Date ();
Response. write (objTest (obj ));