Everything You Need To Know To Master Typing Functions in TypeScript

The ultimate guide to mastering the art of typing functions in TypeScript, equipped with all the necessary tools and knowledge to ensure your success.

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Too many function syntaxes are available, even when writing JavaScript. Sometimes this can be very confusing. So how can we type these functions with TypeScript?

Today we will study this topic. Let’s get started.

1. Function Declarations
2. Function Expressions
3. Optional and Default Parameters
4. Rest Parameters
5. Methods for Object properties
6. Methods for Classes
7. Async Functions

Function Declarations

function addNumbers(x: number, y: number): number {
 return x + y
}

Function Expressions

Named Function Expression

let addNumbers = function addNumbers(x: number, y: number): number {
 return x + y
}

Anonymous Function Expression

let addNumbers = function (x: number, y: number): number {
 return x + y
}

Using explicit return for arrow functions

let addNumbers = (x: number…