BigInt Literal Support in Earlier ECMAScript Versions

[Vessel9817]

🔍 Search Terms

BigInt literals ES2020

✅ Viability Checklist

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
• This isn't a request to add a new utility type: https://github.com/microsoft/TypeScript/wiki/No-New-Utility-Types
• This feature would agree with the rest of our Design Goals: https://github.com/Microsoft/TypeScript/wiki/TypeScript-Design-Goals

⭐ Suggestion

In ES versions >= ES2016 and < ES2019, the transpiler should convert BigInt literals to their equivalent object instantiation. This proposal implements backwards compatibility for BigInt literals, seemingly without any technical or logistical challenges.

Playing devil's advocate, this proposal could technically be considered syntactical sugar, as it brings no further functionality to TypeScript. However, it is conversely a JavaScript feature whose support could be extended.

📃 Motivating Example

The following sample works fine in ES2016:

BigInt('-5') ** BigInt('3') // BigInt('-125')

This isn't very readable, given that JavaScript implements a shorthand that should be easily implementable:

(-5n) ** 3n // -125n

💻 Use Cases

1. What do you want to use this for?

This proposal would resolve the following TS error:

BigInt literals are not available when targeting lower than ES2020. ts(2737)

Note that this compatibility resolution should not affect the following error in any capacity:

Exponentiation cannot be performed on 'bigint' values unless the 'target' option is set to 'es2016' or later. ts(2791)

2. What shortcomings exist with current approaches?

Syntactical bloat, and potential tiny performance losses from instantiating separate BigInt objects over using literals.

3. What workarounds are you using in the meantime?

Instead of BigInt literals (e.g, 5n), use the BigInt constructor (e.g, BigInt('5')).

[Renegade334]

The BigInt constructor also didn't exist prior to ES2020?

[MartinJohns]

The following sample works fine in ES2016:

But it doesn't. As Renegade mentioned, BigInt was introduced in ES2020. If you have a runtime supporting only ES2016 then the code will crash.

[Josh-Cena]

Well a runtime polyfill could be installed. TS already does this for well-known symbols (assume that a polyfill is in place).