JavaScript Tutorial
JavaScript Numbers
In JavaScript, numbers are used to represent integer and decimal values. Unlike some languages, JavaScript uses one number type for both whole numbers and floating-point numbers.
Creating Numbers
let age = 25;
let price = 99.99;
let temperature = -5;
JavaScript numbers can be:
- Positive
- Negative
- Whole numbers (integers)
- Decimal numbers (floats)
Number Data Type
let x = 10;
console.log(typeof x); // number
All numeric values in JavaScript belong to the Number data type.
Arithmetic with Numbers
let a = 10;
let b = 5;
console.log(a + b); // 15
console.log(a - b); // 5
console.log(a * b); // 50
console.log(a / b); // 2
console.log(a % b); // 0
Special Number Values
NaN (Not a Number)
let result = "abc" / 2;
console.log(result); // NaN
Infinity
console.log(10 / 0); // Infinity
console.log(-10 / 0); // -Infinity
Converting Strings to Numbers
Number()
Number("100"); // 100
Number("abc"); // NaN
parseFloat()
parseFloat("10.5"); // 10.5
Checking Numbers
isNaN()
isNaN("hello"); // true
isNaN(10); // false
Number.isInteger()
Number.isInteger(10); // true
Number.isInteger(10.5); // false
Rounding Numbers
Math.round(4.6); // 5
Math.floor(4.9); // 4
Math.ceil(4.1); // 5
Fixed Decimal Places
let num = 12.3456;
num.toFixed(2); // "12.35"
Returns a string, not a number.
Math Object (Common Methods)
Math.max(10, 20, 30); // 30
Math.min(5, 3, 9); // 3
Math.sqrt(16); // 4
Math.pow(2, 3); // 8
Math.random(); // Random number (0–1)Random Numbers Example
// Random number between 1 and 10
Math.floor(Math.random() * 10) + 1;
Number Limits
Number.MAX_VALUE;
Number.MIN_VALUE;
These represent the largest and smallest possible numbers in JavaScript.
Common Mistakes
Treating numbers as strings
Number("10") + 5; // 15
Convert before calculation
Number("10") + 5; // 15
Best Practices
- Always validate numeric input
- Convert user input to numbers
- Use Math methods for calculations
- Be careful with floating-point precision