# JavaScript Math
# float and money
JavaScript Numbers are IEEE 754 64-bit floating point. The result is that we can't safely add money because the decimal will get skewered by floating point rounding errors.
.2 + .1 === .3; // false
1
# the money problem
Floating Point Numbers & Currency Rounding Errors - Patrick Bacon - 20140814
Don’t use floating point numbers for money
Ways it Can Go Wrong :
- During Calculations
- During Storage
- During Retrieval
- Before Display
stackoverflow comment explaining the problem
# quicks solutions
# toFixed()
using Number.prototype.toFixed() - stackoverflow.com / MDN
Warning toFixed returns a string. This to prepare display in UI not to do maths.
# do calculation on cents
just represent all monetary values using an integer number of the smallest relevant units of the currency