Category: JavaScript

This solution is summarized from an archived support forum post. This information may have changed. If you notice an error, please let us know in Discord.

Sum of values with reduce


I am confused about the Javascript result of a code that uses the reduce function on an array of numbers. The result is not what I expected and has extra decimal places. I learned that this is due to Javascript encoding numbers as double precision floating point numbers following the IEEE 754 standard. I am wondering if there is a workaround to get the expected result, which involves multiplying the numbers by 10, while still using the reduce function. For now, I am using the toFixed method as a quick and dirty solution.


The problem is that Javascript stores all numbers as double precision floating point numbers, which can result in small rounding errors. To address this, one solution is to multiply the numbers by 10 and then divide by 10 at the end. However, this can be problematic if the numbers are large or if there are many of them.

Another solution is to use the toFixed() method to round the result to the desired number of decimal places. For example, if the desired result is 2 decimal places, you can use the following code:

const data = datatable.reduce((acc, bill) => bill + acc);
return data.toFixed(2);

This will round the result to 2 decimal places and return a string, which can then be converted to a number if needed.

Overall, the best solution will depend on the specific requirements of the application and the nature of the data being processed.