Phase 6 — Numbers

JavaScript Numbers & Math Object

Numbers are one of the most commonly used data types in JavaScript. Whether you're building a shopping cart, calculator, dashboard, game, or analytics application, you'll frequently work with numbers.

JavaScript provides:

• Number methods for formatting and conversion.
• Math object for mathematical calculations.
• Random number generation.
• Rounding functions.
• Parsing functions.

Math Object

The Math object provides built-in mathematical constants and functions.

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1console.log(Math.PI);

Output

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13.141592653589793

Math.random()

Generates a random decimal number between 0 (inclusive) and 1 (exclusive).

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1console.log(Math.random());

Example Output

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10.548329

Random Integer (1–10)

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1const random = Math.floor(Math.random() * 10) + 1;
2
3console.log(random);

Math.round()

Rounds to the nearest integer.

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1console.log(Math.round(4.4));
2console.log(Math.round(4.6));

Output

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14
25

Math.floor()

Rounds down to the nearest integer.

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1console.log(Math.floor(4.9));

Output

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14

Math.ceil()

Rounds up to the nearest integer.

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1console.log(Math.ceil(4.1));

Output

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15

Math.trunc()

Removes the decimal part.

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1console.log(Math.trunc(7.89));

Output

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17

Math.max()

Returns the largest number.

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1console.log(Math.max(10, 50, 20));

Output

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150

Math.min()

Returns the smallest number.

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1console.log(Math.min(10, 50, 20));

Output

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110

Math.abs()

Returns the absolute (positive) value.

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1console.log(Math.abs(-25));

Output

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125

Math.pow()

Raises a number to a power.

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1console.log(Math.pow(2, 3));

Output

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18

Modern JavaScript also supports:

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1console.log(2 ** 3);

Math.sqrt()

Returns the square root.

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1console.log(Math.sqrt(64));

Output

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18

Math.sign()

Returns the sign of a number.

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1console.log(Math.sign(-20));
2console.log(Math.sign(0));
3console.log(Math.sign(50));

Output

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1-1
20
31

Math.PI

Represents the value of π.

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1const radius = 5;
2
3const area = Math.PI * radius * radius;
4
5console.log(area);

Number.toFixed()

Formats a number with fixed decimal places.

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1const price = 123.4567;
2
3console.log(price.toFixed(2));

Output

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1123.46

Number.toPrecision()

Formats a number using a specified precision.

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1const num = 123.456;
2
3console.log(num.toPrecision(4));

Output

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1123.5

parseInt()

Converts a string into an integer.

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1console.log(parseInt("100"));
2console.log(parseInt("100px"));

Output

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1100
2100

parseFloat()

Converts a string into a floating-point number.

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1console.log(parseFloat("99.95"));

Output

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199.95

isNaN()

Checks whether a value is Not-a-Number.

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1console.log(isNaN("Hello"));
2console.log(isNaN(100));

Output

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1true
2false

isFinite()

Checks whether a number is finite.

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1console.log(isFinite(100));
2console.log(isFinite(Infinity));

Output

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1true
2false

Mini Project — Random Dice Roller

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1const dice = Math.floor(Math.random() * 6) + 1;
2
3console.log(`Dice: ${dice}`);

Possible Output

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1Dice: 4

Best Practices

• Use Math.floor(Math.random() * n) to generate random integers.
• Prefer the exponent operator (**) over Math.pow() in modern JavaScript.
• Use toFixed() for displaying currency values.
• Use parseInt() and parseFloat() to convert user input from forms.
• Validate numeric input with isNaN() or Number.isNaN() before performing calculations.

Summary

In this tutorial, you learned:

• How to use the Math object.
• How to generate random numbers.
• Different rounding methods (round(), floor(), ceil(), trunc()).
• How to find minimum and maximum values.
• How to calculate powers and square roots.
• How to format numbers using toFixed() and toPrecision().
• How to convert strings into numbers with parseInt() and parseFloat().
• How to validate numeric values using isNaN() and isFinite().

Next Module: Phase 7 — Dates & Time, where you'll learn the JavaScript Date object, timestamps, formatting, time zones, and date manipulation used in real-world applications.