---
id: 587d7b84367417b2b2512b34
title: Use typeof to Check the Type of a Variable
challengeType: 1
---
## Description
You can use typeof to check the data structure, or type, of a variable. This is useful in debugging when working with multiple data types. If you think you're adding two numbers, but one is actually a string, the results can be unexpected. Type errors can lurk in calculations or function calls. Be careful especially when you're accessing and working with external data in the form of a JavaScript Object Notation (JSON) object.
Here are some examples using typeof:
console.log(typeof ""); // outputs "string"
console.log(typeof 0); // outputs "number"
console.log(typeof []); // outputs "object"
console.log(typeof {}); // outputs "object"
JavaScript recognizes six primitive (immutable) data types: Boolean, Null, Undefined, Number, String, and Symbol (new with ES6) and one type for mutable items: Object. Note that in JavaScript, arrays are technically a type of object.
## Instructions
Add two console.log() statements to check the typeof each of the two variables seven and three in the code.
## Tests
```yml
tests:
- text: Your code should use typeof in two console.log() statements to check the type of the variables.
testString: assert(code.match(/console\.log\(typeof[\( ].*\)?\)/g).length == 2, 'Your code should use typeof in two console.log() statements to check the type of the variables.');
- text: Your code should use typeof to check the type of the variable seven.
testString: assert(code.match(/typeof[\( ]seven\)?/g), 'Your code should use typeof to check the type of the variable seven.');
- text: Your code should use typeof to check the type of the variable three.
testString: assert(code.match(/typeof[\( ]three\)?/g), 'Your code should use typeof to check the type of the variable three.');
```
## Challenge Seed
```js
let seven = 7;
let three = "3";
console.log(seven + three);
// Add your code below this line
```
## Solution
```js
let seven = 7;let three = "3";console.log(typeof seven);
console.log(typeof three);
```