Precision & Random Values

Floating-point

Decimals can produce tiny precision differences.

Integer units

Store exact quantities as integers when possible.

Math.random

Useful for non-secure random UI behavior.

Crypto random

Use Web Crypto for security-sensitive randomness.

Round display output

Good for visible percentages and approximate values.

const value = 0.1 + 0.2;

console.log(value.toFixed(2)); // "0.30"

Use integer units

Avoid decimal drift by calculating in smaller whole units.

const centsA = 10;
const centsB = 20;
const totalCents = centsA + centsB;

console.log(totalCents); // 30

Random integer range

The common non-secure pattern for simple UI use.

function randomInt(min, max) {
  return Math.floor(Math.random() * (max - min + 1)) + min;
}

console.log(randomInt(1, 6));

Secure random id

Use browser crypto for values that should not be predictable.

const id = crypto.randomUUID();

console.log(id);

Expect decimal drift

Tiny floating-point differences are normal for many decimals.

Round only for display

Rounding hides display noise but should not define core data rules by accident.

Use integer units for exact values

Whole-unit calculations are easier to keep exact.

Use Math.random only for non-secure randomness

It is not for tokens, passwords or security decisions.

Use crypto for secure randomness

Web Crypto provides stronger browser randomness.

Document range helpers

Random range functions should clearly define inclusive and exclusive bounds.

Production note

Production code should separate approximate display math from exact business rules and use secure randomness for security-sensitive values.

SEO note

Random rendering should not change important content, headings or links in ways that make pages inconsistent for crawlers and users.