Registry / web-framework / babel-plugin-transform-proxy-compat

babel-plugin-transform-proxy-compat

library0.22.4jsnpmunverified

Babel plugin that rewrites property lookups, assignments, deletions, function invocations, 'in' statements, and 'for...in' loops to use function calls from a proxy-compat library, enabling Proxy semantics in environments like IE 11 that lack native Proxy support. Current stable version is 0.22.4, with maintenance-level releases. Key differentiator: allows using modern Proxy-based reactivity or interceptors while targeting legacy browsers without polyfilling Proxy itself. Typically paired with libraries like `proxy-compat` that provide the runtime helper functions.

web-framework

npm install babel-plugin-transform-proxy-compat

package ↗

INSTALL

IMPORT

SIG · BABEL-PLUGIN-TRANS

babel-plugin-transform-proxy-compat

web-frameworkjavascriptv0.22.4

Install

—

Import

—

Disk

—

Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

babel-plugin-transform-proxy-compat

✓ import plugin from 'babel-plugin-transform-proxy-compat';

✗ const plugin = require('babel-plugin-transform-proxy-compat');

CommonJS require works; this plugin is not ESM-only.

callKey

✓ import { callKey } from 'proxy-compat';

✗ import callKey from 'proxy-compat';

callKey is a named export from proxy-compat; default export is the whole module.

ProxyCompat

✓ import ProxyCompat from 'proxy-compat';

✗ const ProxyCompat = require('proxy-compat').default;

CommonJS users should use const ProxyCompat = require('proxy-compat'); (no .default)

Configures Babel to transform Proxy operations to use proxy-compat runtime for IE 11 compatibility.

// babel.config.js module.exports = { plugins: [ ['babel-plugin-transform-proxy-compat', { resolveProxyCompat: { module: 'proxy-compat' } }] ] }; // source.js const obj = new Proxy({}, { get(target, prop) { return prop in target ? target[prop] : 42; } }); console.log(obj.foo); // becomes: console.log(callKey(obj, 'foo'));

Debug

Known issues

gotchaPlugin rewrites ALL object property access, assignment, deletion, and 'in'/'for...in' expressions, even if not related to a Proxy. This can cause significant code bloat and performance degradation.

fix

Use /* proxy-compat-disable */ comment at top of files that are performance-sensitive and do not use Proxy.

affects: *

breakingOption 'resolveProxyCompat' changed from accepting a string to an object with module/global/independent properties (v0.16+).

fix

Update config to use { module: '...' } or { global: '...' } instead of just a string.

affects: >=0.16 <0.22

deprecatedThe 'polyfill' option was removed in favor of 'resolveProxyCompat' (v0.10+).

fix

Use resolveProxyCompat with module or global sub-option.

affects: >=0.10 <0.16

gotchaWhen using 'global' mode, the global variable must be defined before the transformed code runs. The plugin does not inject a polyfill.

fix

Ensure a global variable (e.g., window.MyProxyCompat) is defined via a script tag or other means.

affects: *

gotchaPlugin does not transform property access on literals (e.g., 'abc'.length) or built-in objects like Array.prototype. Only object property access is transformed.

fix

Be aware that some property accesses may not be rewritten; test thoroughly.

affects: *

Errors

Common errors & fixes

Error: Could not find module 'proxy-compat'

The runtime dependency 'proxy-compat' is not installed.

fix

Run: npm install proxy-compat --save

TypeError: callKey is not a function

Using 'independent' mode but importing the wrong export.

fix

Change import to: import callKey from 'proxy-compat/callKey'; (not from 'proxy-compat')

TypeError: ProxyCompat.callKey is undefined

Using CommonJS require without the correct import pattern.

fix

Use: const ProxyCompat = require('proxy-compat'); (no .default)

Upgrade

Version history

0.22.4latest on npm

Audit

Dependencies

proxy-compatrequiredRuntime module that provides the actual proxy-compat functions (callKey, getKey, setKey, etc.) when using module or independent modes.

Agent activity

16 hits · last 30 days

node

Amazon

OpenAI (training)

Resources

packagehttps://www.npmjs.com/package/babel-plugin-transform-proxy-compat ↗