@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

v7.25.9 (2024-10-22)

:bug: Bug Fix

• babel-parser, babel-template, babel-types
  • #16905 fix: Keep type annotations in syntacticPlaceholders mode (@liuxingbaoyu)
• babel-helper-compilation-targets, babel-preset-env
  • #16907 fix: support BROWSERSLIST{,_CONFIG} env (@JLHwung)
• Other
  • #16884 Analyze ClassAccessorProperty to prevent the no-undef rule (@victorenator)

:house: Internal

• babel-helper-transform-fixture-test-runner
  • #16914 remove test options flaky (@JLHwung)

:running_woman: Performance

• babel-parser, babel-types
  • #16918 perf: Make VISITOR_KEYS etc. faster to access (@liuxingbaoyu)