json-replace-exponentials

This module provides a function which takes a JSON string and replaces all numbers in exponential notation. By default, numbers in exponential notation are replaced by numbers in fixed-point notation. If an optional replacer function is provided, its return value is used instead.

The primary motivation for this module is to produce JSON for programs which handle exponential notation incorrectly (e.g. Azure/autorest#3006).

Introductory Example

Using the CLI:

json-replace-exponentials <input-exponentials.json >output-fixed.json

Using the API:

const { readFile, writeFile } = require('fs').promises;
const jsonReplaceExponentials = require('json-replace-exponentials');

readFile('input-exponentials.json', { encoding: 'utf8' })
  .then((json) => writeFile(
    'output-fixed.json',
    JSON.stringify(jsonReplaceExponentials(json), undefined, 2),
  );

Features

• Preserves white-space and formatting of input JSON.
• Preserves full precision of replaced numbers, even for numbers which can not be exactly represented by the JavaScript number type.
• The default replacer throws RangeError for numbers where the exponential is larger than 1,000 or smaller than -1,000 to mitigate unexpected result size increases for large fixed-point representations. Warning: Consider this risk when using a custom replacer.

Non-Features

• Does not parse or validate input JSON. If input is not valid JSON, the behavior of json-replace-exponentials is undefined.

Installation

This package can be installed using npm, either globally or locally, by running:

npm install json-replace-exponentials

Recipes

Replace large exponents

As noted above, by default, exponents larger than 1,000 or -1,000 cause RangeError to be thrown. To replace with (non-standard) Infinity and Underflow, and others with the default replacement:

const jsonReplaceExponentials = require('json-replace-exponentials');

function replacer(exponential) {
  const match = /[eE]([+-]?)[0-9]{4,}$/.exec(exponential);
  if (match) {
    return match[1] === '-' ? 'Underflow' : 'Infinity';
  }

  return jsonReplaceExponentials(exponential);
}

jsonReplaceExponentials(json, replacer);

API Docs

To use this module as a library, see the API Documentation.

Contributing

Contributions are appreciated. Contributors agree to abide by the Contributor Covenant Code of Conduct. If this is your first time contributing to a Free and Open Source Software project, consider reading How to Contribute to Open Source in the Open Source Guides.

If the desired change is large, complex, backwards-incompatible, can have significantly differing implementations, or may not be in scope for this project, opening an issue before writing the code can avoid frustration and save a lot of time and effort.

License

This project is available under the terms of the MIT License. See the summary at TLDRLegal.