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Number and Math

Learn Number methods and the Math object.

Number and Math

In JavaScript, all numbers are of type number; there is no separate integer and decimal type. The Math object provides ready-made functions for common math operations.

For example, Math.max(3, 9, 5) returns the largest value; Math.min(3, 9, 5) the smallest. Math.floor(3.7) rounds down, Math.ceil(3.2) rounds up.

Math.round(3.5) rounds to the nearest integer. These functions make number operations easy.

Number conversions

To convert a string to a number, you use the Number(...) function. For example, Number('42') returns the number 42.

If the string does not look like a number, the result is NaN (Not-a-Number). For example, Number('hello') returns NaN.

This is very useful when converting user input to numbers, especially from command-line arguments.

Practice Find the largest with Math.max

Declare three numbers: a = 12, b = 45, c = 7. Find the largest with Math.max(a, b, c) and print it with console.log.

Starter code

index.js
const a = 12;
const b = 45;
const c = 7;
// Find the largest with Math.max and log it

Sample solution

index.js
const a = 12;
const b = 45;
const c = 7;
console.log(Math.max(a, b, c));

Expected output

45

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Using Math.max

Question 
const largest = Math.max(3, ____);
Answer 
const largest = Math.max(3, 9);

Explanation: Math.max returns the largest number.

2 Match the Math functions

Term Meaning
Math.max Largest
Math.min Smallest
Math.floor Round down
Math.round Nearest integer

3 What does Number("42") return?

  • The string '42'
  • Throws an error
  • undefined
  • The number 42 Correct answer

Explanation: Number('42') returns the number 42.

All lessons in Beginner

1 Node.js basics

  1. What is Node.js?
  2. Your first program
  3. ES modules
  4. package.json
  5. CommonJS vs ESM
  6. Summary - Node.js basics

2 Variables

  1. let and const
  2. var and scope
  3. Type inference
  4. Destructuring
  5. Spread and rest
  6. Summary - Variables

3 Data types

  1. Primitive types
  2. Template literals
  3. Number and Math
  4. Symbol
  5. typeof
  6. Summary - Data types

4 Project: Calculator

  1. Project design
  2. Add and subtract
  3. Multiply and divide
  4. process.argv
  5. Putting it together

5 Operators

  1. Arithmetic operators
  2. Assignment operators
  3. Comparison operators
  4. Logical operators
  5. Nullish coalescing
  6. Summary - Operators

6 Strings

  1. String methods
  2. String search
  3. substring and slice
  4. replace and split
  5. padStart and trim
  6. Summary - Strings

7 Conditionals

  1. The if statement
  2. else and else if
  3. switch
  4. Ternary
  5. Optional chaining
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. The while loop
  3. for...of
  4. for...in
  5. break and continue
  6. Summary - Loops

9 Project: Shopping cart

  1. Cart design
  2. Adding items
  3. Calculating totals
  4. Listing the cart
  5. Putting it together

10 Arrays

  1. Declaring arrays
  2. Array access
  3. push and pop
  4. shift and unshift
  5. splice and slice
  6. Summary - Arrays

11 Array methods

  1. map
  2. filter
  3. reduce
  4. find and some
  5. forEach
  6. Summary - Array methods

12 Objects

  1. Object literal
  2. Property access
  3. Computed properties
  4. Object methods
  5. Object spread
  6. Summary - Objects

13 Functions

  1. Defining functions
  2. Return values
  3. Arrow functions
  4. Default parameters
  5. Rest parameters
  6. Summary - Functions

14 Callbacks

  1. What are callbacks?
  2. Higher-order functions
  3. forEach with callbacks
  4. Error-first callbacks
  5. Callback hell
  6. Summary - Callbacks

15 Project: To-do CLI

  1. Task model
  2. Adding tasks
  3. Listing tasks
  4. Completing tasks
  5. Putting it together

16 Promises

  1. What are promises?
  2. then and catch
  3. Promise.all
  4. Promise.race
  5. finally
  6. Summary - Promises

17 async/await

  1. async function
  2. await
  3. try/catch
  4. await with Promise.all
  5. Sequential await
  6. Summary - async/await

18 fs module

  1. fs.promises
  2. readFile
  3. writeFile
  4. appendFile
  5. existsSync
  6. Summary - fs module

19 path module

  1. path.join
  2. path.resolve
  3. path.parse
  4. path.dirname and basename
  5. path.extname
  6. Summary - path module

20 Beginner final

  1. Project design
  2. Data model
  3. Business logic
  4. fs persistence
  5. Putting it together