JavaScript Syntax

JavaScript Syntax

Welcome to our JavaScript Syntax tutorial! As you begin your journey in learning JavaScript, understanding the basic syntax is a crucial first step. Syntax refers to the rules and conventions that govern how JavaScript code should be written and structured.

In this tutorial, we’ll cover the fundamentals of JavaScript syntax, including variables, operators, expressions, and control structures. We’ll also discuss comments and whitespace, along with best practices for writing clean and maintainable JavaScript code. By the end of this tutorial, you’ll have a solid foundation in JavaScript syntax, enabling you to write and read JavaScript code with confidence.

Overview of JavaScript Syntax

JavaScript syntax refers to the set of rules that define how JavaScript programs are constructed. Understanding the syntax is crucial for writing valid and functional JavaScript code. Some fundamental aspects of JavaScript syntax include variables, data types, operators, and control structures.

Variable Syntax in JS

Variables are used to store values in JavaScript. You can declare variables using the var, let, or const keywords.


var aVar = "Hello, world!";
let aLet = "Hello, world!";
const aConst = "Hello, world!";

Data Type Syntax in JS

JavaScript has several data types, including:

  • Number: Represents numeric values
  • String: Represents text
  • Boolean: Represents true or false values
  • Object: Represents collections of properties
  • Array: Represents ordered lists of values
  • Function: Represents executable code blocks
  • Null: Represents an intentionally empty value
  • Undefined: Represents a variable that has not been assigned a value


const num = 42;
const str = "Hello, world!";
const bool = true;
const obj = { firstName: "John", lastName: "Doe" };
const arr = [1, 2, 3];
const func = function() { console.log("Hello, world!"); };
const empty = null;
let notAssigned;


JavaScript has various operators for performing operations on values, such as:

  • Arithmetic operators: +, -, *, /, %
  • Comparison operators: ==, ===, !=, !==, <, >, <=, >=
  • Logical operators: &&, ||, !
  • Assignment operators: =, +=, -=, *=, /=, %=


const a = 10;
const b = 5;

console.log(a + b); // Output: 15
console.log(a === b); // Output: false
console.log(a > b && a < 20); // Output: true

Control Structures

Control structures are used to control the flow of execution in JavaScript code. Some common control structures include:

  • Conditional statements: if, else, else if
  • Loops: for, while, do...while
  • Switch statement


const num = 42;

if (num > 40) {
  console.log("Number is greater than 40");
} else {
  console.log("Number is not greater than 40");

for (let i = 0; i < 5; i++) {

while (num > 0) {

Practice Questions about Syntax in JS

  1. What are the different ways to declare variables in JavaScript?
  2. What are some common data types in JavaScript?
  3. What are some common JavaScript operators?
  4. What are some common JavaScript control structures?


Q: What is JavaScript syntax?

A: JavaScript syntax refers to the set of rules that define how JavaScript programs are constructed. It includes variables, data types, operators, and control structures.