Step 2: Data Types

If you played around with console.log() in the last step, you might have noticed that words always have to be inside quotes or else the code breaks, whereas numbers can work without quotes. Why is this? Well there are different data types in JavaScript. We're going to learn the three main data types right now (later we'll look at some other data types, like objects and arrays).


A string is just a bit of text, ranging anywhere from a single character to lengthy paragraphs. A string is always written inside a pair of quotes (single or double).

"node girls"


Numbers are known as "integers" in JavaScript. They do not need to be wrapped in quotes like strings, and can just be written as is.



There is a special data type in JavaScript known as a "boolean" value. It denotes if a statement is true or false. It can have a value of either true or false, and is always written without quotes.


Try it out

You've seen what they look like, now make sure they are what you think they are. There is a built-in feature in JavaScript which allows you to check the type of a particular value: typeof.

Write this code in your Repl, and click "run":

console.log(typeof "Hello world!");

You should see string printed to the console. That's because 'Hello world!' is a string data type.

Mini challenge

Now try that three times, once for each data type. Log the typeof three different values: "node girls", 1234 and false. You should get different output for each one.