30 Days of javascript Challenge

JavaScript Variables and Data Types

Day 1: Variables and Data Types in JavaScript

1. Variable Declaration:

• var Keyword:

  • Used for declaring variables that are function-scoped or globally-scoped.
  • Example:

    var num1 = 19;
    console.log(num1); // Outputs: 19

• let Keyword:

  • Introduces block-scoped variables, replacing var in modern JavaScript.
  • Example:

    let name = "Jay Prajapati";
    console.log(name); // Outputs: "Jay Prajapati"

2. Constant Declaration:

• const Keyword:
  • Declares constants that cannot be reassigned.
  • Example:

    const isLoggedIn = true;
    console.log(isLoggedIn); // Outputs: true

3. Data Types:

JavaScript supports several primitive and reference data types:

• Primitive Data Types:

  • Number: Represents numeric values.

    let myNumber = 42;
    console.log(typeof myNumber); // Outputs: "number"

  • String: Represents textual data enclosed in quotes.

    let myString = "Hello, world!";
    console.log(typeof myString); // Outputs: "string"

  • Boolean: Represents a logical entity with values true or false.

    let myBoolean = true;
    console.log(typeof myBoolean); // Outputs: "boolean"

  • Undefined: Represents a variable that has been declared but not assigned a value.

    let myUndefined;
    console.log(typeof myUndefined); // Outputs: "undefined"

  • Null: Represents the intentional absence of any object value.

    let myNull = null;
    console.log(typeof myNull); // Outputs: "object" (known issue in JavaScript)

  • Symbol: Represents a unique identifier.

    let mySymbol = Symbol("symbol");
    console.log(typeof mySymbol); // Outputs: "symbol"

  • BigInt: Represents integers larger than 2^53 - 1 or smaller than -2^53 - 1.

    let myBigInt = 12345678901234567890n;
    console.log(typeof myBigInt); // Outputs: "bigint"

• Reference Data Types:

  • Object: Represents instances through properties and methods.

    let myObject = { name: "Alice", age: 30 };
    console.log(typeof myObject); // Outputs: "object"

  • Array: Represents a list of items, accessed by index.

    let myArray = [1, 2, 3, 4, 5];
    console.log(typeof myArray); // Outputs: "object"

  • Function: A callable object that executes a block of code.

    let myFunction = function () {
      return "This is a function";
    };
    console.log(typeof myFunction); // Outputs: "function"

Day 2: Operators

Task 1: Add Two Numbers

const num1 = 10;
const num2 = 20;
const sum = num1 + num2;
console.log(sum); // Output: 30

num1 and num2 are initialized with values 10 and 20, respectively. sum stores the result of adding num1 and num2. The console.log(sum) statement outputs the result 30.

Task 2: Subtract Two Numbers

const num3 = 20;
const num4 = 10;
const difference = num3 - num4;
console.log(difference); // Output: 10

• Explanation: num3 and num4 are initialized with values 20 and 10, respectively. difference stores the result of subtracting num4 from num3. The console.log(difference) statement outputs the result 10.