Why when I am cast this string "2019275.159999999916180968" to number, or when used parseFloat(str). I'm always get result "2019275.16". Why it remove extra decimal places that provided in the string? And how can i keep number of decimal places, without rounding it to 2 decimal places in this case?
Amount of decimal places in the string is dynamical.
It might be worth investigating a library like decimal.js to help with this. e.g.:
Decimal.set({ precision: 24 }); // The default of 20 is not big enough for the number below so you may need to adjust this
let a = new Decimal('2019275.159999999912345');
a = a.plus(1);
let b = new Decimal('2019275.159999999912345').plus(1);
let c = Decimal.add('2019275.159999999912345', 1);
console.log(a, b, c);<script src="https://cdnjs.cloudflare.com/ajax/libs/decimal.js/9.0.0/decimal.min.js"></script>You can use toFixed() method after parseFloat() otherwise it will return least precision equivalent to internal representation
parseFloat("2019275.159999999916180968").toFixed(18)