Hello, JavaScript!

What you'll learn

Print something with console.log()
Create variables with let and const
Build text with template strings

JavaScript – the language of the web

Every website that moves, reacts to clicks or offers games in the browser uses JavaScript. It runs in every browser – this editor runs your code directly too.

Not related to Java: despite the name, JavaScript has almost nothing to do with the language Java. In 1995 the name was a marketing trick because Java was all the rage.

Your first program

In JavaScript, printing is called console.log():

console.log("Hello, world!");
console.log(7 * 6);
console.log("I am", 12, "years old");

Most statements end with a semicolon ;. It’s often not required, but it’s good style.

Variables: let and const

const name = "Mia";      // const: never changes
let points = 10;         // let: may change
points = points + 5;
console.log(name, points);

const for values that stay the same – that’s the normal case.
let when the value should change later.

Try changing name later – JavaScript complains!

Building text

You can join text with +. More convenient are template strings in backticks (`). Inside them, ${…} inserts values:

const animal = "cat";
const count = 3;
console.log("I have " + count + " " + animal + "s.");
console.log(`I have ${count} ${animal}s.`);
console.log(`In 5 years I'll be ${12 + 5}.`);

Python comparison: template strings are like f-strings in Python: f"I am {age}" ↔ `I am ${age}`.

Quick check

What does this program print?

let x = 4;
x = x * 2 + 1;
console.log(`x is ${x}`);

Your task

Your turn

Create two constants: name with your name and age with your age. Then print exactly this sentence with one template string (backticks ` ` and ${…}): My name is Mia and I am 12 years old.` – with your values, of course.

// Create name and age here

console.log("Hello!");

Something to think about
For example, write const name = "Mia"; and const age = 12;
Which command helps?
Watch every character – including the full stop at the end.
A template string is written in backticks: `My name is ${name} …`

Gap code – fill in the ___

                        const name = ___;
const age = ___;
console.log(___);

Solve it without hints to earn a ⭐ on your progress page.

Show solution

Try it yourself first – mistakes teach you the most. Here is one possible solution:

const name = "Mia";
const age = 12;
console.log(`My name is ${name} and I am ${age} years old.`);