Date & Math

In real-world applications, time and calculations are everywhere. We track dates, calculate prices, generate random values, and round numbers for display.

JavaScript provides built-in tools like the Date object and the Math object to handle these tasks easily.

Working with Dates

The Date object is used to work with dates and times. It can represent the current date or a specific date.

Creating a Date

You can create a date using the new Date() constructor.

let today = new Date();
  

This stores the current date and time.

Getting Date Information

JavaScript provides methods to extract parts of a date.

let now = new Date();

now.getFullYear();
now.getMonth();
now.getDate();
  

These methods help display readable dates to users.

Real-World Date Example

Imagine showing today’s date on a dashboard:

let date = new Date();
let message =
  date.getDate() + "/" +
  (date.getMonth() + 1) + "/" +
  date.getFullYear();

console.log(message);
  

Dates are widely used in logs, reports, and scheduling systems.

The Math Object

The Math object provides useful mathematical functions. You do not need to create it — it is available by default.

Common Math Methods

Math.round(4.6);
Math.floor(4.9);
Math.ceil(4.1);
Math.random();
  

These methods are commonly used in pricing, scoring, and random selection.

Real-World Math Example

Imagine generating a random discount:

let discount =
  Math.floor(Math.random() * 10) + 1;

console.log("Discount:", discount + "%");
  

This logic is often used in promotions and games.

Common Beginner Mistakes

• Forgetting that months start from 0
• Using Math.random() without a range
• Manually calculating values instead of using Math methods

Built-in methods reduce errors and improve clarity.

Thumb Rules

• Use Date for all date and time operations
• Remember that months are zero-based
• Use Math methods instead of manual calculations
• Keep date formatting user-friendly

More on Date & Math Later

This lesson covered basic usage of Date and Math objects.

More advanced handling is covered later.

• Timers and scheduling are explained in Lesson 24 (Timers)
• Advanced calculations appear in real-world projects later

What Comes Next?

Now that you can work with dates and calculations, it’s time to handle errors safely.

In the next lesson, we will learn about error handling.