Best way to prevent/handle divide by 0 in javascript

Question

What is the best way to prevent divide by 0 in javascript that is accepting user inputs. If there is no particular way to achieve this what would be the best way to handle s

Answer 1

The best way is contextual. But here's the easiest:

function myFunction( input ){
    input = 0 ? 0.0001 : input; // same as if( input == 0 ){ input = 0.0001; }
    return 1 / input;
}

Basically if the input is zero, turn it into a very small number before using as a denominator. Works great for integers, since after your division you can round them back down.

A couple caveats prevent this from being universal:

• It could cause false positives if your input accepts really small numbers
• It won't trigger any error-handling code, if you need to do something special if zero is entered

So it's best for general-purpose, non-critical cases. For example, if you need to return the result of a complex calculation and don't care if the answer is accurate to N digits (determined by 0.0001 vs. 0.00000001, etc.); you just don't want it to break on a divide-by-zero.

As another answer suggested, you could also create a reusable global function.

function divisor( n ){ return ( n = 0 ? 0.0001 : n ); }
function myFunction( input ){ return 1 / divisor( input ); }

Possible improvements:

function divisor( n, orError ){
    if( typeof n == 'undefined' || isNaN( n ) || !n ){
        if( orError ){ throw new Error( 'Divide by zero.' ); }
        return 0.000000000000001;
    }else{ return 0 + n; }
}

This would take any value (null, number, string, object) and if invalid or zero, return the failsafe zero-like value. It would also coerce the output to a number just in case it was a string and you were doing something odd. All this would ensure that your divisor function always worked. Finally, for cases where you wanted to handle such errors yourself, you could set the second parameter to true and use a try/catch.