Understanding of NULL, Undefined, Nan equivalents, and data types in JS

The data types in JavaScript are null, undefined, number, String, Boolean, object six. The first five are basic data types,

object is a reference type that includes an array, function, and so on.

First Test the types of the various values

var A1;
var a2 = true;
var a3 = 0;
var a4 = "Hello";
var A5 = new Object ();
var a6 = null;
var a7 = NaN;
var a8 = undefined;
Alert (typeof a); Show "Undefined"
Alert (typeof A1); Show "Undefined"
Alert (typeof A2); Show "Boolean"
Alert (typeof A3); Show "Number"
Alert (typeof A4); Show "string"
Alert (typeof A5); Show "Object"
Alert (typeof A6); Show "Object"
Alert (typeof A7); Show "Number"
Alert (typeof A8); Show "Undefined"

A type of Undefined,nan with a type of number,null that is visible from the undefined variable type is object. Let's do the comparison test again,

var A1;
var a2 = null;
var a3 = NaN;
var a4 = true;
var A5 = "true";
var a6 = 0;
var a7 = undefined;

alert (a1 = = A2); Show "true"
alert (a1 = = A3); Show "false"
alert (A2 = = A3); Show "false"
Alert (a3 = = A3); Show "false"
alert (A2 = = = a3);//display "false"
alert (a4 = = A5);//display "false"
alert (A2 = = A6);//display "false"
alert (a1 = = a7);//Display "true"
alert (A2 = = a7);//Display "true"

Null and undefined equivalents can be seen but not congruent, null and 0 are not equivalent, true and "true" are not equivalent, and Nan is not equal to any value including itself.

Understanding of NULL, Undefined, Nan equivalents, and data types in JS