Javascript Module 18

  Module 18 : Math Object and Number Methods 

 JavaScript Math Object and Number Methods

🔷 Part 1: Math Object

The Math object in JavaScript is a built-in object that has properties and methods for mathematical constants and functions. Unlike other global objects, Math is not a constructor, so you don’t create Math objects.

🔹 Common Math Methods

Method

Description

Example

Math.abs(x)

Returns the absolute (positive) value of x

Math.abs(-4.7) ➝ 4.7

Math.ceil(x)

Rounds x up to the nearest integer

Math.ceil(4.4) ➝ 5

Math.floor(x)

Rounds x down to the nearest integer

Math.floor(4.7) ➝ 4

Math.round(x)

Rounds x to the nearest integer

Math.round(4.5) ➝ 5

Math.max(a, b, …)

Returns the highe

Math.max(1, 5, 10) ➝ 10

st number

Math.min(a, b, …)

Returns the lowest number

Math.min(1, 5, 10) ➝ 1

Math.random()

Returns a pseudo-random number between 0 and 1

Math.random() ➝ 0.234…

Math.pow(x, y)

Returns x to the power of y

Math.pow(2, 3) ➝ 8

Math.sqrt(x)

Returns the square root of x

Math.sqrt(16) ➝ 4

Math.trunc(x)

Returns integer part of x by removing decimals

Math.trunc(4.9) ➝ 4

📘 Example

javascript

code

function calculateAreaOfCircle(radius) { return Math.PI * Math.pow(radius, 2); } console.log(calculateAreaOfCircle(5)); // ➝ 78.53981633974483

🔷 Part 2: Number Methods

JavaScript provides methods that can be used with number values.

🔹 Common Number Methods

Method

Description

Example

toFixed(n)

Formats number with n decimals (returns string)

(12.3456).toFixed(2) ➝ "12.35"

toPrecision(n)

Formats number to n significant digits

(123.456).toPrecision(4) ➝ "123.5"

toString([radix])

Converts number to a string (optional radix)

(255).toString(16) ➝ "ff"

Number.isFinite(x)

Checks if x is a finite number

Number.isFinite(5) ➝ true

Number.isInteger(x)

Checks if x is an integer

Number.isInteger(5.1) ➝ false

Number.parseFloat(x)

Parses a string and returns a floating-point number

Number.parseFloat("10.33") ➝ 10.33

Number.parseInt(x)

Parses a string and returns an integer

Number.parseInt("10.33") ➝ 10

📘 Example

javascript  code

function formatCurrency(amount) { return "$" + amount.toFixed(2); } console.log(formatCurrency(9)); // ➝ "$9.00" console.log(formatCurrency(9.567)); // ➝ "$9.57"

🎓 Exercises

🔹 Exercise 1: Generate a Random Integer Between 1 and 100

javascript

code

function getRandomInt1to100() { return Math.floor(Math.random() * 100) + 1; } console.log(getRandomInt1to100());

🔹 Exercise 2: Format and Validate a User Input

javascript

code

function validateAndFormat(input) { let num = Number.parseFloat(input); if (Number.isFinite(num)) { return num.toFixed(2); } else { return "Invalid number!"; } } console.log(validateAndFormat("123.456")); // ➝ "123.46" console.log(validateAndFormat("abc")); // ➝ "Invalid number!"

🔹 Exercise 3: Find Min and Max from User Input

javascript

 code

function findMinMax(...numbers) { return { min: Math.min(...numbers), max: Math.max(...numbers) }; } console.log(findMinMax(4, 8, 1, 99, 0)); // ➝ { min: 0, max: 99 }

🧠  Notes

Math vs. Number:

Math is a namespace with utility functions.

Number methods work on number values or Number objects.

Precision Issues:

JavaScript uses floating-point arithmetic (IEEE 754), which can lead to rounding errors.

Use toFixed() or libraries like BigInt/Decimal.js for high precision needs.

Security Tip:

Never use Math.random() for cryptographic purposes. Use crypto.getRandomValues() in secure contexts.

🧑‍🏫  Plan

Introduction:

Define Math and Number in JavaScript.

Clarify their differences with diagrams.

Demonstration:

Use live coding tools to show  output.

Challenge  with edge cases (e.g., Math.floor(-1.5)).

Practice Time:

Divide  into groups to build a calculator that uses at least 3 Math and 2 Number methods.

Q&A and Wrap-up:

Discuss common pitfalls.

Hand out a quiz (e.g., "What does parseInt('12.34') return?").