VarData

Author: anup-sys

Basics/Datatypes.js

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+let name = "Anup" //String
+let age = 21; //number
+let isStudent = true; //boolean
+let x = "10";
+console.log([name,age,isStudent,x])
+console.table([name,age,isStudent,x])
+
+let a; //undefined
+let b = null; //null
+
+let age1 = 25;               // number
+let name1 = "Anup";          // string
+let isLoggedIn = true;      // boolean
+let user;                   // undefined
+let car = null;             // null
+let id = Symbol("unique");  // symbol
+let bigNumber = 12345678901234567890n; // bigint
+
+let person = {
+    name : "Anup",
+    age : 21,
+    isStudent : true,
+}
+
+let subjects = ["Math","Science","English"];
+
+function greet() {
+    console.log("Welcome " + person.name);
+}
+console.log(typeof 10);         // "number"
+console.log(typeof "Hello");    // "string"
+console.log(typeof true);       // "boolean"
+console.log(typeof undefined);  // "undefined"
+console.log(typeof null);       // "object"  ❗ (known JS bug)
+console.log(typeof Symbol());   // "symbol"
+console.log(typeof 123n);       // "bigint"
+
+console.log(typeof NaN);
+
+let data = 10;
+data = 'anup';
+data = true;
+
+let x1;
+console.log(x1); // logs "undefined"
+
+console.log(x); // ReferenceError
+const x2 = 3;
+
+console.log(y); // ReferenceError
+let y = 3;
+
+//Example 1 – Number + String → String
+
+let result = 5 + "10"
+console.log(result);
+console.log(typeof result);

Basics/DatatypesConv.js

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+// Example 1 – Number + String → String    //Implicit Type Conversion (Type Coercion)   //
+let result = 5 + "10"
+console.log(result);
+console.log(typeof result);
+
+let result1 = "10";          //JavaScript automatically converts one data type to another during expression evaluation.
+console.log(result1)
+console.log(typeof result1)
+
+//Example 2 – String → Number (when using -, *, /)
+
+console.log("10" - 2);
+console.log("10"/2);
+console.log("10"*2);
+
+console.log(10/2);
+console.log(10*2);
+console.log(10-2);
+
+//Example 3 – Boolean Conversion
+
+console.log(true + 1);  //true hereis 1
+console.log(false + 1); //false here is 0
+
+//Example 4 – Non-Numeric String
+
+console.log("Abc" - 2);
+
+let ABC;
+console.log(typeof ABC);
+
+
+//Explicit Type Conversion (Manual)
+
+//You can manually convert data types using built-in JavaScript functions.
+
+//Convert to String
+
+let num = 100;
+console.log(String(num))
+console.log(num.toString())
+
+let num1 = 100;
+
+let str = String(num1);
+console.log(str);
+console.log(typeof str);
+
+let x = 10 + "";
+console.log(x);        // "10"
+console.log(typeof x); // "string"
+
+let y = true + "";
+console.log(y);        // "true"
+
+
+//Real-Life Example
+
+let age =  25;
+let message = "I am " + age  + " Year Old";
+console.log(message)
+
+
+//Convert to number
+
+let str1 = "123";
+let num2 = Number(str1);
+console.log(num2);        // 123
+console.log(typeof num2); // number
+
+console.log(Number("10"))
+console.log(typeof Number) //function
+
+
+console.log(typeof null); //object
+console.log(typeof undefined);  //undefined
+
+
+//Convert to Boolean
+console.log(Boolean(0));         // false
+console.log(Boolean(""));        // false
+console.log(Boolean("Hello"));   // true
+console.log(Boolean(123));       // true

Basics/Variable.js

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+const accountID = 14567;
+let accountPassword = "Fg123";
+let accountEmail = "ghty@gmail.com";
+let accountCity = "Bengaluru";
+
+console.log(accountID);
+
+accountEmail = "newemail@gmail.com";
+accountPassword = "fgrt123";
+// accountID = 23456; ❌ (Not allowed, since it's const)
+
+console.table([accountEmail, accountCity, accountPassword, accountID]);
+
+
+
+let name = "Anup"
+console.log(name)
+
+var city = "Bengaluru"
+console.log(city)
+
+var city1 = "Mumbai"
+city1 = "Bnegaluru"
+console.log(city1)
+
+let age = 26
+console.log(age)
+
+let ageboy = 24
+ageboy = 26
+console.log(ageboy)
+
+const country = "India";
+// country = "USA"; ❌ Error: Assignment to constant variable
+console.log(country);
+
+
+/*
+Prefer not to use var
+because in issue of block scope and  functional scope
+*/
+