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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.