Using the typeof operator in Javascript



April 17, 2020

It's Fridayy 🔥🔥
Ready for a JavaScript tip?

Today we'll talk about the 'typeof' operator in JavaScript. Basically this operator lets us check what type a variable has. This can be super helpful in some scenarios, let's check it.

const num = 24; const string = 'webDevTips'; const func = () => true; var undef; const obj = { name: 'John Doe', age: 44 }; console.log(typeof num) // -> number console.log(typeof string) // -> string console.log(typeof func) // -> function console.log(typeof undef) // -> undefined console.log(typeof obj) // -> object

On the first code snippet we have some variables with different types - string, number, function, undefined and object. To check wich type they have we just need to do 'typeof ourVar'. This will return the correct type this variable has.

// Using this in conditions // If this 'func' is actually a function, we will run it if (typeof func === 'function') { func(); }

On the second snippet we see how we can implement this in a real world scenario. We have the 'func' variable that we expect to be a function. Still, before we run it we might want to check it it's actually a function so we create an if statement where we use 'typeof' to make sure that we are dealing with a function. If that's the case, we'll execute it.

Hope you have a great weekend guys, take care! 😎✌