JavaScript typeof Operator
New Course Coming Soon:
Get Really Good at Git
Learn the basics of the JavaScript typeof Operator
In JavaScript, any value has a type assigned.
The typeof
operator is a unary operator that returns a string representing the type of a variable.
Example usage:
typeof 1 //'number'
typeof '1' //'string'
typeof {name: 'Flavio'} //'object'
typeof [1, 2, 3] //'object'
typeof true //'boolean'
typeof undefined //'undefined'
typeof (() => {}) //'function'
typeof Symbol() //'symbol'
JavaScript has no “function” type, and it seems funny that typeof
returns 'function'
when we pass it a function.
It’s one quirk of it, to make our job easier.
If you don’t initialize the variable when you declare it, it will have the undefined
value until you assign a value to it.
let a //typeof a === 'undefined'
typeof
works also on object properties.
If you have a car
object, with just one property:
const car = {
model: 'Fiesta'
}
This is how you check if the color
property is defined on this object:
if (typeof car.color === 'undefined') {
// color is undefined
}
Are you intimidated by Git? Can’t figure out merge vs
rebase? Are you afraid of screwing up something any time
you have to do something in Git? Do you rely on ChatGPT
or random people’s answer on StackOverflow to fix your
problems? Your coworkers are tired of explaining Git to
you all the time? Git is something we all need to use,
but few of us really master it. I created this course to
improve your Git (and GitHub) knowledge at a radical
level. A course that helps you feel less frustrated with
Git. Launching Summer 2024. Join the waiting list!
→ Get my
JavaScript Beginner's Handbook
→ Read my
JavaScript Tutorials
on The Valley of Code
→ Read my
TypeScript Tutorial
on The Valley of Code
Here is how can I help you:
- COURSES where I teach everything I know
- THE VALLEY OF CODE your web development manual
- BOOTCAMP 2024 cohort in progress, next edition in 2025
- BOOKS 16 coding ebooks you can download for free on JS Python C PHP and lots more
- SOLO LAB everything I know about running a lifestyle business as a solopreneur
- Interesting links collection
- Follow me on X