toFixed(2) rounds “x.525” inconsistently?

Question

I\'m experiencing rounding errors when using toFixed:

I used toFixed(2) on my numeric value calculations, but the rounding results are not as expected

Answer 1

Use Intl.NumberFormat and in options set minimumFractionDigits and maximumFractionDigits to the same number (number of digits you want to display).

const formatter = [0, 1, 2, 3, 4, 5].map(
    (decimals) =>
        new Intl.NumberFormat('en-US', {
            minimumFractionDigits: decimals,
            maximumFractionDigits: decimals,
        }),
);

console.log(formatter[2].format(17.525)); // 17.53
console.log(formatter[2].format(5.525)); // 5.53
console.log(formatter[2].format(1.005)); // 1.01
console.log(formatter[2].format(8.635)); // 8.64
console.log(formatter[2].format(8.575)); // 8.58
console.log(formatter[2].format(35.855)); // 35.86
console.log(formatter[2].format(859.385)); // 589.39
console.log(formatter[2].format(859.3844)); // 589.38
console.log(formatter[2].format(.004)); // 0.00
console.log(formatter[2].format(0.0000001)); // 0.00

// keep in mind that this will not be formatted as expected, as the value that
// you pass is actually 0.07499999999998863. 
console.log(formatter[2].format(239.575 - 239.5)); // 0.07
console.log(formatter[2].format(0.07499999999998863)); // 0.07

Answer 2

Floating point inaccuracy means that most numbers ending .525 are actually .52500..1, and others are .5249999.....

Which way the value rounds depends on whether the closest actual representation in IEEE-754 floating point is above or below the desired value.

Answer 3

Instead of toFixed() use Math.ceil() , Math.floor() or Math.round()

with a way around like

var rnum = 5.525,
    decimalPlaces = 2,
    factor = Math.pow(10, decimalPlaces),
    newnumber = Math.round(rnum * factor) / factor,
    mydecimalvalue = parseFloat(newnumber); 

the result is 5.53

Answer 4

Convert the number to String and work with it?

That is the last resort after I have tried to use Math.round, or simulate the nearest rounding with Math.ceil, but failed. When multiplying with 100, some number (such as 17.525) will be a bit less than 100 times its value (1752.5), while other numbers (such as 17.545) will be a bit more than 100 times its value (1754.5).