Strings, numbers, booleans, objects and more.
✍️ 3 exercises + code challenge in this lessonJavaScript has 8 data types:
"Hello"42, 3.149007199254740993ntrue or falseJavaScript is dynamically typed: the same variable can hold different types. Use typeof to check a type.
Mastering JavaScript Data Types helps you write clean and reliable JavaScript code. Follow standard conventions, test edge cases, and keep logic simple. Try running the code example below and complete the exercises to build confidence.
<pre id="out"></pre>
<script>
const log = (...a) => document.getElementById("out").textContent += a.join(" ") + "\n";
let value;
log(typeof value); // undefined
value = "text"; log(typeof value);
value = 42; log(typeof value);
value = true; log(typeof value);
value = { a: 1 }; log(typeof value);
value = [1, 2]; log(typeof value, "(arrays are objects)");
value = null; log(typeof value, "(a famous JavaScript quirk)");
log(typeof 10n);
</script>Check what you learned in “JavaScript Data Types”.
Find out the type of a value.
"hello" // "string"
What does typeof null return?
This is a well-known historical quirk of JavaScript.
Log the type of the value 42.
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