Why should you care?

Adding "5" + "3" gives "53" (string concat). Adding 5 + 3 gives 8 (math). Knowing types prevents silent bugs.

See it live — copy this example

Paste into an HTML file or the browser console (F12). Use Run below when the live editor is available.

console.log(typeof "hello");
console.log(typeof 42);
console.log(typeof true);
console.log(typeof undefined);
let person = { name: "Amit", age: 22 };
console.log(typeof person);

Run Example »

Edit the code below and click Run to see the result in Toolliyo’s live editor.

What happened?

• Strings use quotes.
• Numbers have no quotes.
• typeof returns a string naming the type.
• Objects hold grouped data — person is an object.

Practice next

1. Run each typeof line in the console.
2. Try typeof null and note the quirk.
3. Create let x; without assigning and check typeof x.
4. Add typeof for a function: typeof function(){}.
5. Create a bigint with 100n and log typeof 100n.

Remember

typeof shows the type Use quotes for strings, not for numbers Objects group related data

ScriptVerse API validation

A form handler checks typeof age === "number" before saving a profile — strings from inputs would break math otherwise.

Outcome: Type checks at boundaries catch bad data before it reaches the database.