Numbers
JavaScript has a single number type for integers and decimals.
Syntax
let n = 42;
let price = 9.99;JavaScript has one number type for both whole numbers and decimals — there is no separate integer type.
Special values
Infinity— a value larger than any number.NaN— "Not a Number", the result of an invalid math operation.
Example
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Press Run to execute the code.
When to use it
- Round a floating-point price to two decimal places before displaying it in the checkout summary.
- Check for NaN after parsing a user-supplied string to prevent silent calculation errors.
- Represent very large or very small scientific values (e.g. distances in space) using numeric literals.
More examples
Integer and float arithmetic
Multiplies a float price by an integer quantity and formats the result to two decimal places.
const price = 19.99;
const qty = 3;
const total = price * qty;
console.log(total.toFixed(2)); // "59.97"NaN and Infinity
Shows how division by zero produces Infinity or NaN, and how to check for these with isNaN/isFinite.
console.log(0 / 0); // NaN
console.log(1 / 0); // Infinity
console.log(isNaN("hello")); // true
console.log(isFinite(42)); // trueNumber() conversion and precision
Demonstrates Number() conversion results and the classic floating-point precision issue.
console.log(Number("3.14")); // 3.14
console.log(Number("")); // 0
console.log(Number("abc")); // NaN
console.log(0.1 + 0.2); // 0.30000000000000004 – float precision
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