In JavaScript, division by zero does not cause an error. Instead, it evaluates to Infinity, which is a reserved word (note the capital “I”). To see this, run the following code:

alert(5/0);

You’ll get an alert that reads “Infinity”, which is a number:

alert(typeof Infinity); //number
alert(isNaN(Infinity)); //false

You can check for an infinite number using the isFinite() function:

isFinite(5/0); //false

There is also negative infinity:

alert(-5/0); //-Infinity

Finally, numbers that are too big or too small for JavaScript to handle evaluate to Infinity:

alert(Math.pow(10,309)); //Infinity