datatypes.js

function show(x) { console.log(x) }
function line(x) { console.log(`line ${x} --> `) }

//8 Data Types 
//-------------------------------------------
//1 - number
// some special number NaN , Infinity , -Infinity
show(typeof (Infinity));
show(`line 9 --> ${typeof (NaN)}`);

// 2. NaN represent a computational error 
show("string" / 3);

// NaN is sticky 
show("string" / 2 + 5 - 8);
//or
show(2 + 3 / "String")

//------------------------------
// bigint --- number is limited to 2^53
// made by adding 'n' at last of a number
show(`line 22 --> ${typeof (134567890n)}`)

// 3. String 
let str1 = "can be written in double Quote"
let str2 = 'also can be written in single quote'
//backticks can use expression and variable too
let something = "backticks"
let str = `in ${something} also`

show(str)

// 4. boolean - true / false value only 

let isBun = true;
line(36)
show(typeof (isBun))

let isNPM = false;
show(typeof isNPM)

// also come as result of  comparison 
line(43)
show(5 < 3);

// 5. Null
// A value purposely or implicitely set empty , Nothing
// or unknown
let value = null;
line(50)
show(typeof value) // wrong in js it is actually null

// 6. undefined
// meaning value is not set/assigned
let aVar;
line(56)
show(aVar)

// undefined can be value also 
let var2 = undefined;
line(61);
show(var2)

// But null is preferred not undefined

let var23 = null;
line(67)
show(var23)

///// ---- typeof operator
// typeof operator returns va;lue as string 

//used in 2 form  
// typeof value
// typeof (value)
// only works with a operand
line(77)
show(typeof undefined);
show(typeof (2345678));
show(typeof 3456789n);
show(typeof true);
show(typeof "foo");
show(typeof Symbol("id"));
show(typeof Math);
show(typeof null);//wrong in js
show(typeof alert);