floating point - Why does modulus operator return fractional number in javascript?

Question

Why does 49.90 % 0.10 in JavaScript return 0.09999999999999581? I expected it to be 0.

Answer 1

Because JavaScript uses floating point math which can lead to rounding errors.

If you need an exact result with two decimal places, multiply your numbers with 100 before the operation and then divide again afterwards:

var result = ( 4990 % 10 ) / 100;

Round if necessary.