TypeScript provides many powerful methods to work with data types, including ReturnType, which helps us get the Return Type of a Function. The article will show you how to do it. Let’s start together.
Get the return Type of a Function in TypeScript.
While working, you want to avoid hardcoding types in your code that can lead to errors but want to rely on a data type returned from a function. You can use ReturnType Utility and typeof
operator.
ReturnType Utility Type
ReturnType in TypeScript language takes the return data type and constructs a new type. It is very useful when a function wants to receive data returned from another function.
Example:
In this example, we create a function that returns the string data type and then passes it to ReturnType. The newType variable will receive the return data type from the ReturnType and create a student variable with the newType data type.
// Use ReturnType to get the data type type newType = ReturnType<() => string>; const student: newType = "John"; console.log(typeof student);
Output:
string
Use ReturnType with the typeof type operator.
In JavaScript, you can use typeof
to check the type in an expression context.
Example:
const name = "John"; // Using typeof in JavaScript console.log(typeof name);
Output:
string
In TypeScript, you can use typeof
to refer to the data type of a variable
Example:
let student = "John"; // Using typeof in TypeScript let newType: typeof student;
newType will be of type string because of the reference from the student variable.
Combining the two, we can get the return Type of a Function in TypeScript
Example:
const GetName = (): string => { return "John"; }; // Using ReturnType with typeof type newType = ReturnType<typeof GetName>;
newType will have a data type of string
To refer to the data type of the function GetName, we use the keyword typeof. Combined with the ReturnType utility, we will get the data type of the function and store it in the newType variable
Get the return type of an asynchronous function
For the asynchronous function, we need to use Awaited utility to wait for Promise to return from the function.
Example:
async function GetAPI(url: string) { const data = fetch(url); return data; } // Use Awaited utility to wait for Promise to return from the function type newType = Awaited<ReturnType<typeof GetAPI>>;
newType will have a data type of promise
Summary
The article have show you how to get the return Type of a Function in TypeScript using ReturnType and typeof
. Use it, and you will see no need to do many updates in the program. Please comment if you have any questions, we will be happy to answer.

Carolyn Hise has three years of software development expertise. Strong familiarity with the following languages is required: Python, Typescript/Nodejs, .Net, Java, C++, and a strong foundation in Object-oriented programming (OOP).