json-parse-immutable

Stage 2
Classification: Syntactic Change Semantic Change
Human Validated: KW
Title: JSON.parseImmutable
Authors: Robin Ricard, Richard Button, Nicolò Ribaudo, Ashley Claymore
Champions: Robin Ricard, Richard Button, Nicolò Ribaudo, Ashley Claymore
Last Presented: July 2022
Stage Upgrades:
Stage 1: NA
Stage 2: 2022-07-28
Stage 2.7: NA
Stage 3: NA
Stage 4: NA
Last Commit: 2022-07-28
Topics: objects json performance
Keywords: json parse performance tuple record
GitHub Link: https://github.com/tc39/proposal-json-parseimmutable
GitHub Note Link: https://github.com/tc39/notes/blob/main/meetings/2022-07/jul-19.md#conclusiondecision-2

Proposal Description:

JSON.parseImmutable Proposal

Status

Stage 2

Champions:

• Robin Ricard (Bloomberg)
• Rick Button (Bloomberg)
• Nicolò Ribaudo (Igalia)
• Ashley Claymore (Bloomberg)

Overview

This proposal complements the record-tuple proposal. It was originally part of that proposal but split off into a separate proposal to reduce the scope of the core Records and Tuples proposal. #330

The problem being explored is ergonomic and efficient creation of a deeply immutable data structure from a JSON string.

JSON.parse(data, (key, value) => {
  if (typeof value === 'object' && value !== null) {
      if (Array.isArray(value)) {
        return Tuple.from(value);
      } else {
        return Record(value);
      }
  }
  return value;
});

Could be replaced with:

JSON.parseImmutable(data);