Rest parameters with types in Typescript - Mini Project: Build & Apply

Rest parameters with types

📖 Scenario: You are building a simple calculator that can add any number of numbers together.Users will give you many numbers, and you want to add them all up.

🎯 Goal: Create a function that uses rest parameters with types to accept any number of numbers and returns their sum.

📋 What You'll Learn

Create a function called sumNumbers that uses rest parameters with type number[].

Inside the function, add all the numbers together.

Call the function with multiple numbers.

Print the result.

💡 Why This Matters

🌍 Real World

Functions with rest parameters are useful when you don't know how many inputs you will get, like adding many numbers or combining many strings.

💼 Career

Understanding rest parameters and types is important for writing flexible and type-safe functions in TypeScript, a skill valuable for many programming jobs.

1

Create the function with rest parameters

Write a function called sumNumbers that takes rest parameters named numbers with type number[].

Typescript

// Your code here

Need a hint?

Use ...numbers: number[] to accept many numbers as an array.

2

Add the numbers inside the function

Inside the sumNumbers function, create a variable called total set to 0. Then use a for loop with variable num to add each number in numbers to total.

Typescript

function sumNumbers(...numbers: number[]) {
  // Create total variable and add numbers
  // Your code here
}

Need a hint?

Use a for...of loop to add each number to total.

3

Call the function with multiple numbers

Call the sumNumbers function with the numbers 5, 10, and 15, and store the result in a variable called result.

Typescript

function sumNumbers(...numbers: number[]) {
  let total = 0;
  for (let num of numbers) {
    total += num;
  }
  return total;
}

// Call sumNumbers with 5, 10, 15
// Your code here

Need a hint?

Call the function with the numbers separated by commas inside the parentheses.

4

Print the result

Write a console.log statement to print the value of the variable result.

Typescript

function sumNumbers(...numbers: number[]) {
  let total = 0;
  for (let num of numbers) {
    total += num;
  }
  return total;
}

const result = sumNumbers(5, 10, 15);

// Print the result
// Your code here

Need a hint?

Use console.log(result) to show the sum.