Knockout.Validation中的浮点舍入错误

Question

I have an numeric input with a step of 0.01 that is "watched" by Knockout and has the Knockout.validation plugin also checking the value.

When testing the input to make sure that it is giving appropriate error messages, I found that certain input will result in a validation message. For example, the value -0.14 will result in the error: "The value must increment by 0.01".

The offending Knockout.Validation code is:

return utils.isEmptyVal(val) || (val * 100) % (step * 100) === 0;

For val = -0.14 with step = 0.01 , floating point arithmetic causes this line to return false, meaning that Knockout.Validation sees -0.14 as an invalid input. This is just an example, there are many cases where this happens. For the -0.14 case, the result of (val * 100) % (step * 100) is -1.7763568394002505e-15 .

Is there an easy way I can patch this code? Would the following suffice under all circumstances:

return utils.isEmptyVal(val) || parseInt(val * 100) % parseInt(step * 100) === 0;

Or should I have a range check?

Answer 1

In a similar situation, I found the code in this issue fixed my problem.

The core code in question seems very similar to your proposed solution, although I assume there is a good reason to use parseFloat rather than parseInt.