জাভাস্ক্রিপ্ট ভেরিয়েবল এবং ডেটা টাইপ

Variables

• A variable is a container that holds a value.
• In JavaScript, variables are declared using the let, const, or var keywords.
• let and const are block-scoped, while var is function-scoped.
• Variables can be reassigned, except for those declared with const.
• Variables can be initialized with a value or left undefined.

Data Types

• Primitive Data Types:
  • Number: 42 or 3.14
  • String: "hello" or 'hello'
  • Boolean: true or false
  • Null: null
  • Undefined: undefined
• Complex Data Types:
  • Object: { key: value, ... }
  • Array: [ element, ... ]
  • Function: function() { ... }

Functions

• A function is a block of code that can be executed multiple times.
• Functions can take arguments and return values.
• Functions can be declared using the function keyword or as an arrow function.
• Functions can be assigned to variables or passed as arguments to other functions.

Conditional Statements

• If Statement:
  • if (condition) { code }
  • Executes code if condition is true
• If-Else Statement:
  • if (condition) { code } else { code }
  • Executes code if condition is true, otherwise executes else code
• Switch Statement:
  • switch (expression) { case value: code; break; ... }
  • Executes code based on the value of the expression

Loops

• For Loop:
  • for (init; condition; increment) { code }
  • Executes code repeatedly while condition is true
• While Loop:
  • while (condition) { code }
  • Executes code repeatedly while condition is true
• Do-While Loop:
  • do { code } while (condition)
  • Executes code at least once, then repeats while condition is true
• For-Of Loop:
  • for (variable of iterable) { code }
  • Executes code for each element in the iterable
• For-In Loop:
  • for (variable in object) { code }
  • Executes code for each property in the object