Programs Step by Step

Programs run from top to bottom, one line at a time. Let's learn how to do math and build text!

Doing Math

JavaScript can do math with these operators:

javascript

console.log(3 + 2); // Addition: 5

console.log(10 - 4); // Subtraction: 6

console.log(3 * 5); // Multiplication: 15

console.log(10 / 3); // Division: 3.3333...

console.log(10 % 3); // Remainder: 1

Output

Press Run to see the output.

Careful: // is NOT division in JavaScript — it starts a comment! To divide and drop the decimal part, use Math.floor():

javascript

console.log(Math.floor(10 / 3)); // Integer division: 3

Output

Press Run to see the output.

Math with Variables

You can store numbers and compute results:

javascript

let width = 5;

let height = 3;

let area = width * height;

console.log(area);

Output

Press Run to see the output.

Output:

Building Strings

You can join strings together with +:

javascript

let first = "Hello";

let second = "World";

let message = first + " " + second;

console.log(message);

Output

Press Run to see the output.

Output:

Hello World

Template Literals

Template literals are the easiest way to mix text and variables. Use backticks ` instead of quotes, and ${variable} to insert values:

javascript

let name = "Alex";

let age = 10;

console.log(`Hello, ${name}! You are ${age} years old.`);

Output

Press Run to see the output.

Output:

Hello, Alex! You are 10 years old.

The backtick key is usually in the top-left corner of your keyboard, under Esc.

Order of Operations

JavaScript follows math rules — multiplication and division happen before addition and subtraction:

javascript

console.log(2 + 3 * 4); // 14, not 20

console.log((2 + 3) * 4); // 20, parentheses first

Output

Press Run to see the output.