Basic Syntax and Operations in JavaScript

Understanding the basic syntax and operations of JavaScript is crucial for writing efficient and effective code. This guide will introduce you to the foundational elements of JavaScript, including variables, data types, operators, and basic syntax rules.

Variables

Variables are used to store data that can be referenced and manipulated in your program. In JavaScript, you can declare variables using var, let, or const.

• var: Declares a variable, optionally initializing it to a value. It has function scope.
• let: Declares a block-scoped local variable, optionally initializing it to a value.
• const: Declares a block-scoped constant, which must be initialized at the time of declaration and cannot be reassigned.

var name = 'John';
let age = 25;
const isStudent = true;

Data Types

JavaScript supports various data types, which can be broadly categorized into primitive types and objects.

• Primitive Types:
  • String: Represents textual data. Example: 'Hello, World!'
  • Number: Represents numeric values. Example: 42
  • Boolean: Represents logical values, either true or false. Example: true
  • Undefined: Represents a variable that has been declared but not assigned a value.
  • Null: Represents the intentional absence of any object value.
  • Symbol: Represents a unique and immutable value, often used as object keys.
• Objects:
  • Complex data structures that can store collections of data and more complex entities.

Operators

Operators are symbols that perform operations on variables and values. Here are some of the most commonly used operators:

• Arithmetic Operators: +, -, *, /, % (modulus), ++ (increment), -- (decrement)

  let a = 10;
  let b = 5;
  console.log(a + b); // 15
  console.log(a - b); // 5

• Assignment Operators: =, +=, -=, *=, /=, %=

  let x = 10;
  x += 5; // x is now 15

• Comparison Operators: ==, === (strict equality), !=, !== (strict inequality), >, <, >=, <=

  let c = 10;
  console.log(c == '10'); // true
  console.log(c === '10'); // false

• Logical Operators: && (and), || (or), ! (not)

  let isTrue = true;
  let isFalse = false;
  console.log(isTrue && isFalse); // false
  console.log(isTrue || isFalse); // true

Basic Syntax Rules

1. Case Sensitivity: JavaScript is case-sensitive. This means myVariable and myvariable would be considered different variables.
2. Statements and Semicolons: Each statement in JavaScript should end with a semicolon (;). However, JavaScript can automatically insert semicolons (ASI) in certain situations, but relying on this feature is not recommended.
3. Comments: Comments can be added using // for single-line comments and /* */ for multi-line comments.

   // This is a single-line comment
   /* This is a
      multi-line comment */

Example Code

Here’s a simple example that combines variables, data types, and operators:

let name = 'Alice';
let age = 30;
const isEmployed = true;

if (isEmployed) {
    console.log(name + ' is employed and is ' + age + ' years old.');
} else {
    console.log(name + ' is not employed.');
}