The type of value returned by a function.

What is optional parameter?

A parameter that may or may not be passed.

TypeScript Functions - Learn TYPESCRIPT | Revochamp

Name: TypeScript Functions
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Author: Revochamp

What are Functions?

Functions in TypeScript are blocks of reusable code with optional type annotations for parameters and return values.

Basic Function

TypeScriptRead-only

function add(a: number, b: number): number {
  return a + b;
}

function add(a: number, b: number): number {
  return a + b;
}

Void Function

TypeScriptRead-only

function logMessage(msg: string): void {
  console.log(msg);
}

function logMessage(msg: string): void {
  console.log(msg);
}

Optional Parameters

TypeScriptRead-only

function greet(name?: string) {
  return name || 'Guest';
}

function greet(name?: string) {
  return name || 'Guest';
}

Default Parameters

TypeScriptRead-only

function greet(name: string = 'Guest') {
  return name;
}

function greet(name: string = 'Guest') {
  return name;
}

Arrow Functions

TypeScriptRead-only

const multiply = (a: number, b: number): number => a * b;

const multiply = (a: number, b: number): number => a * b;

Function Types

TypeScriptRead-only

let addFn: (a: number, b: number) => number;
addFn = add;

let addFn: (a: number, b: number) => number;
addFn = add;

Rest Parameters

TypeScriptRead-only

function sum(...nums: number[]): number {
  return nums.reduce((a, b) => a + b, 0);
}

function sum(...nums: number[]): number {
  return nums.reduce((a, b) => a + b, 0);
}

Best Practices

Always define parameter types
Specify return types for clarity
Use default parameters when needed
Keep functions small and reusable

Common Mistakes

Not specifying return types
Incorrect parameter types
Overusing any type
Complex functions without structure

Conclusion

TypeScript functions improve code reliability by enforcing types for parameters and return values, ensuring safer and predictable behavior.

What are Functions?

Functions in TypeScript are blocks of reusable code with optional type annotations for parameters and return values.

Basic Function

TypeScriptRead-only

function add(a: number, b: number): number {
  return a + b;
}

function add(a: number, b: number): number {
  return a + b;
}

Void Function

TypeScriptRead-only

function logMessage(msg: string): void {
  console.log(msg);
}

function logMessage(msg: string): void {
  console.log(msg);
}

Optional Parameters

TypeScriptRead-only

function greet(name?: string) {
  return name || 'Guest';
}

function greet(name?: string) {
  return name || 'Guest';
}

Default Parameters

TypeScriptRead-only

function greet(name: string = 'Guest') {
  return name;
}

function greet(name: string = 'Guest') {
  return name;
}

Arrow Functions

TypeScriptRead-only

const multiply = (a: number, b: number): number => a * b;

const multiply = (a: number, b: number): number => a * b;

Function Types

TypeScriptRead-only

let addFn: (a: number, b: number) => number;
addFn = add;

let addFn: (a: number, b: number) => number;
addFn = add;

Rest Parameters

TypeScriptRead-only

function sum(...nums: number[]): number {
  return nums.reduce((a, b) => a + b, 0);
}

function sum(...nums: number[]): number {
  return nums.reduce((a, b) => a + b, 0);
}

Best Practices

Always define parameter types
Specify return types for clarity
Use default parameters when needed
Keep functions small and reusable

Common Mistakes

Not specifying return types
Incorrect parameter types
Overusing any type
Complex functions without structure

Conclusion

TypeScript functions improve code reliability by enforcing types for parameters and return values, ensuring safer and predictable behavior.

TypeScript Functions

TypeScript Functions

What are Functions?

Basic Function

Void Function

Optional Parameters

Default Parameters

Arrow Functions

Function Types

Rest Parameters

Best Practices

Common Mistakes

Conclusion

Try it yourself

Test Your Knowledge

Frequently Asked Questions

Need help?

TypeScript Functions

TypeScript Functions

What are Functions?

Basic Function

Void Function

Optional Parameters

Default Parameters

Arrow Functions

Function Types

Rest Parameters

Best Practices

Common Mistakes

Conclusion

Try it yourself

Test Your Knowledge

Frequently Asked Questions

Need help?