@babel/plugin-transform-typeof-symbol

What is @babel/plugin-transform-typeof-symbol?

The @babel/plugin-transform-typeof-symbol package is a plugin for Babel, a JavaScript compiler, that ensures the behavior of the 'typeof' operator is spec-compliant when used with symbols. In environments that do not fully support symbols, this plugin transforms 'typeof' checks to a method that can correctly identify 'symbol' types.

What are @babel/plugin-transform-typeof-symbol's main functionalities?

Transform typeof checks for symbols

This code represents the transformation that the plugin applies to 'typeof' checks. It defines a function that can correctly identify symbols, even in environments that do not natively support the 'symbol' type.

var _typeof = function(obj) { return obj && typeof Symbol !== 'undefined' && obj.constructor === Symbol ? 'symbol' : typeof obj; };

Other packages similar to @babel/plugin-transform-typeof-symbol

@babel/plugin-transform-runtime

This package helps to reuse Babel's injected helper code to save on codesize. It includes a typeof helper for symbols, similar to what @babel/plugin-transform-typeof-symbol provides, but it's part of a broader set of transformations.

core-js

Although not a direct alternative, core-js is a modular standard library for JavaScript, which includes polyfills for symbols. It ensures that 'typeof' checks for symbols work correctly in older environments, similar to the goal of @babel/plugin-transform-typeof-symbol.

README

@babel/plugin-transform-typeof-symbol

This transformer wraps all typeof expressions with a method that replicates native behaviour. (ie. returning “symbol” for symbols)

See our website @babel/plugin-transform-typeof-symbol for more information.

Install

Using npm:

npm install --save-dev @babel/plugin-transform-typeof-symbol

or using yarn:

yarn add @babel/plugin-transform-typeof-symbol --dev

Changelog

v7.23.3 (2023-11-09)

:bug: Bug Fix

• babel-plugin-transform-typescript
  • #16071 Strip type-only TS namespaces (@colinaaa)
• babel-generator
  • #16078 Fix indentation when generating comments with concise: true (@liuxingbaoyu)
• babel-compat-data, babel-plugin-bugfix-v8-static-class-fields-redefine-readonly, babel-preset-env
  • #14295 Add a bugfix plugin for https://crbug.com/v8/12421 (@nicolo-ribaudo)
• babel-plugin-transform-object-super
  • #15948 fix: super.x in a loop (@liuxingbaoyu)
• babel-helper-module-transforms, babel-plugin-transform-modules-amd, babel-plugin-transform-modules-commonjs, babel-plugin-transform-modules-umd
  • #16015 fix: handle __proto__ exports name in CJS/AMD/UMD (@magic-akari)

:memo: Documentation

• #16044 docs: Update links in @babel/eslint-parser README (@aryehb)

:house: Internal

• babel-core, babel-preset-env
  • #15988 Refactor handling of modules plugins in preset-env (@nicolo-ribaudo)

:running_woman: Performance

• babel-generator
  • #16061 perf: Improve @babel/generator performance (@liuxingbaoyu)
• babel-traverse
  • #16060 Avoid dynamic dispatch when calling wrapCheck (@yepitschunked)

:microscope: Output optimization

• babel-plugin-transform-computed-properties
  • #6652 Optimize computed properties output (byte-wise) (@Andarist)