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Testing this out, why does this work?

function isAdult( age) { if (age && age >= 18) { return true; } else { return false; }


console.log(isAdult(17.99999999999999)); returns false

console.log(isAdult(17.999999999999999)); returns true

1 Answer

Steven Parker
Steven Parker
229,645 Points

This demonstrates how JavaScript handles it when you exceed the precision limits of stored numbers. Perhaps an even better demonstration is just to log the number directly:

console.log(17.99999999999999);  // shows 17.99999999999999
console.log(17.999999999999999); // shows 18

I found an article you might find interesting online about Overcoming Javascript numeric precision issues.