Why is Javascript\'s toFixed() Method Not Rounding Accurately?

Javascript toFixed Not Rounding Precisely

In Javascript, the toFixed() method is used to format numbers into strings. However, users have encountered unexpected rounding behavior when using this method, specifically in cases where it fails to round up numbers correctly.

The reason behind this rounding discrepancy lies in the underlying floating-point arithmetic used by Javascript. Floating-point numbers can sometimes result in precision errors, especially when working with very small or very large values.

To address this issue, consider the following workaround:

The provided solution suggests using the toFixed10() method, which is a modified version of the original toFixed() method that ensures more accurate rounding. This method rounds the number to 10 decimal places, which is precise enough for most practical applications.

The solution also includes a custom toFixed() function that performs similar rounding using the Math.round() and Math.pow() methods. This function allows you to specify the desired precision, ensuring consistent results across browsers.

Implementation

By incorporating the modified toFixed() method or the custom function in your Javascript code, you can effectively resolve the rounding issue and achieve precise numerical calculations:

function toFixed( num, precision ) {
    return (+(Math.round(+(num + 'e' + precision)) + 'e' + -precision)).toFixed(precision);
}

// Usage:
var number = 859.385;
console.log(toFixed(number, 2)); // Output: "859.39"

Conclusion

By understanding the limitations of Javascript's toFixed() method and employing the aforementioned workaround, programmers can overcome the rounding inaccuracies and ensure reliable numerical calculations in their applications.

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