August 20, 2020
Javascript division by 0
JavaScript Basics
What Happens When You Divide by Zero in JavaScript?
Unlike many languages that throw an error, JavaScript returns special numeric values when you divide by zero. Understanding these edge cases prevents confusing console output and logical bugs in your applications.
Safe but Special
Dividing a finite non-zero number by zero never throws an exception in JavaScript. The runtime returns Infinity or -Infinity instead.
Watch for NaN
Zero divided by zero—or an invalid numeric expression—produces NaN. Always guard calculations with sanity checks.
Division by Zero Outcomes
| Expression | Result | Explanation |
|---|---|---|
10 / 0 |
Infinity | Positive numerator divided by zero returns positive infinity. |
-10 / 0 |
-Infinity | Sign is preserved—negative numerator produces negative infinity. |
0 / 0 |
NaN | Mathematically undefined, so JavaScript returns Not-a-Number. |
1 / Infinity |
0 | When dividing by infinity you approach zero, which is useful for normalization logic. |
Console Examples
Positive Numerator
const numerator = 10;
const denominator = 0;
const result = numerator / denominator;
console.log(result); // Infinity
console.log(Number.isFinite(result)); // falseZero Numerator
const value = 0 / 0;
console.log(value); // NaN
console.log(Number.isNaN(value)); // true
console.log(value === value); // false (NaN is never equal to itself)How to Guard Against Unexpected Results
- Check denominators first:
if (denominator === 0)before performing the division. - Use helper utilities: Create a reusable function that returns
nullor throws when division is invalid. - Normalize Infinity: Replace
Infinitywith a sentinel value when serializing or persisting data. - Avoid NaN propagation: NaN contaminates further calculations—use
Number.isNaN()to guard intermediate values.
Reusable Safe Division Helper
export function safeDivide(numerator, denominator, fallback = null) {
if (denominator === 0) {
return fallback;
}
const value = numerator / denominator;
return Number.isFinite(value) ? value : fallback;
}
// usage
console.log(safeDivide(12, 3)); // 4
console.log(safeDivide(12, 0)); // null
Code
JavaScript Code