How to fix decimals arithmetic in JavaScript

JavaScript can return unexpected results when adding or subtracting decimal numbers, such as 0.1 + 0.2 becoming 0.30000000000000004 or 1.4 - 1 becoming 0.3999999999999999. The page says this is not unique to JavaScript, because computers store data in binary and some decimal values cannot be represented exactly.

It suggests using libraries such as decimal.js, bignumber.js, or big.js. It also shows a workaround that multiplies values by a power of 10, performs the calculation, and divides back, including a reusable sum(a, b, positions) function.

Reading notes

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• Decimal arithmetic can produce long repeating results instead of the expected rounded value.
• The problem comes from binary storage and the limited precision of decimal values in that format.
• Libraries like decimal.js, bignumber.js, and big.js are listed as options.
• A workaround is to scale numbers by a factor such as 100, compute the sum, and then divide again.
• The example function uses toFixed(positions) and Math.pow(10, positions) to handle a chosen number of decimal places.