Why Isn't 0.1 + 0.2 Exactly 0.3 in JavaScript?
In JavaScript, 0.1 + 0.2 doesn’t equal exactly 0.3. This isn’t unique to JavaScript but is a common issue in all programming languages that use binary floating-point arithmetic.
In everyday life, we mostly use the decimal system, where fractions like 1/2, 1/4, 1/5, 1/8, and 1/10 can be precisely represented as decimals. However, fractions like 1/3, 1/6, 1/7, and 1/9 cannot. For example, 1/3 is 0.33333333… continuing infinitely.
Similarly, in binary, only fractions like 1/2, 1/4, 1/8, etc. can be precisely represented, while others like 1/10 (0.1 in decimal) cannot be exactly represented and extend infinitely. Since computer memory is limited, programming languages allocate finite memory to numbers, restricting precision. This limitation causes JavaScript to calculate 0.1 + 0.2 as 0.30000000000000004.
To avoid this issue in practical applications, JavaScript provides methods like toFixed and toPrecision for number operations, allowing us to set our desired precision level, such as rounding to one decimal place.
