Скачать или смотреть Understanding the BigInt to Hex Conversion Issue in JavaScript

Learn how to correctly convert large decimal numbers to hexadecimal strings using `BigInt` in JavaScript, and avoid common pitfalls that lead to data loss.
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Understanding the BigInt to Hex Conversion Issue in JavaScript

JavaScript developers often find themselves grappling with large numbers, especially when dealing with data that exceeds the maximum safe integer limit. This article addresses a common issue that arises while attempting to convert large decimal numbers stored as strings into hexadecimal format using the BigInt type. Specifically, we will explore why the decimal to hex conversion can yield unexpected results and how to fix it.

The Problem Statement

The challenge arises when developers try to convert a large decimal string into its hexadecimal representation. A user reported the following scenario in which the last character of the hexadecimal string was truncated. Here’s the core of the problem:

Input Data: The data consists of a large number, specifically 18446744072635809797, represented as a string.

Expected Output: When converting it to hexadecimal using BigInt(decimalString).toString(16), the expected output was ffffffffc0000005.

Actual Output: The result obtained was ffffffffc0000000, showing that the full value was not preserved.

Understanding the Source of the Issue

The confusion stems from the way JSON handles numbers. When the JSON data is read into JavaScript, if the large number is parsed directly as a number, it cannot be stored accurately due to the limitations of JavaScript's Number type. Let’s break it down further:

Number Limits: The maximum safe integer in JavaScript is 9007199254740991 (Number.MAX_SAFE_INTEGER). Anything beyond this limit cannot be accurately represented as a Number.

Parsing Behavior: When JSON parses the input, it tries to convert the number:

Incorrect: { a: 18446744072635809797 } - JavaScript interprets this as 18446744072635810000, leading to loss of precision.

Correct: { a: "18446744072635809797" } - Enclosing the large number in quotes preserves it as a string.

The Solution

Step 1: Adjust Your JSON Data

To resolve the issue, make sure the JSON file that contains your data has the large number as a string:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Update Your Code to Handle the String Correctly

With the large number stored as a string, you can now correctly convert it using BigInt:

[[See Video to Reveal this Text or Code Snippet]]

By following these steps, you’ll maintain the integrity of your large numbers, ensuring that converting them to hexadecimal provides the exact expected results.

Conclusion

The conversion of large decimal strings to hexadecimal using BigInt can lead to data loss when the numbers are not correctly formatted as strings in JSON. By understanding the limitations of JavaScript Number and properly formatting your JSON input, you can avoid truncation issues and ensure precise mathematical operations in your code.

If you’ve encountered similar issues, consider revisiting your data types and formatting. Happy coding!