es6-shim

library0.35.8jsnpmunverified

The `es6-shim` package provides compatibility shims to enable ECMAScript 6 (Harmony) features in legacy JavaScript environments that lack native support. This includes core language features like `Promise`, `Map`, and `Set`, as well as numerous methods on `String`, `Number`, and `Array` prototypes such as `String.prototype.includes` or `Number.isInteger`. It operates by patching the global scope, making these features available as if they were natively implemented. The current stable version is 0.35.8, which primarily focuses on bug fixes, robustness improvements, and spec compliance. As a polyfill library, its release cadence is driven by bug reports and updates to the ECMAScript specification, rather than frequent feature additions, differentiating it from libraries introducing new paradigms. It aims to make older engines behave as closely as possible to the ES6 standard.

serialization

npm install es6-shim

github ↗package ↗

INSTALL

IMPORT

SIG · ES6-SHIM

es6-shim

serializationjavascriptv0.35.8

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.

Global ES6 Polyfills (Browser)

✓ <script src="node_modules/es6-shim/es6-shim.js"></script>

✗ <script src="es6-shim.js"></script> (if not copied to root), or not loading es5-shim first

Includes all ES6 shims and polyfills into the global scope. Ensure `es5-shim.js` is loaded before this script if needed, typically from `node_modules/es5-shim/es5-shim.js`.

Global ES6 Polyfills (Node.js/CommonJS)

✓ require('es6-shim');

✗ import 'es6-shim'; (Incorrect ES module syntax for this package)

Loads all ES6 shims and polyfills into the global Node.js environment. It is strongly recommended to also `require('es5-shim');` *before* this line for robust polyfilling across various environments.

ES6 Sham (Node.js/CommonJS)

✓ require('es6-shim/es6-sham');

✗ require('es6-shim'); (This only loads the main shim, not the 'sham')

The `es6-sham` file provides shims for features that are not fully compliant with the ES6 spec or have known side effects (e.g., `Function.prototype.name`). Load it explicitly if these specific shims are desired.

Demonstrates how to include `es6-shim` and `es5-shim` and then use various ECMAScript 6 features like `Map`, `Promise`, `String.prototype.includes`, and `Number.isInteger` that are polyfilled by the library.

// In a browser environment, you would include these via script tags in your HTML: // <script src="node_modules/es5-shim/es5-shim.js"></script> // <script src="node_modules/es6-shim/es6-shim.js"></script> // For Node.js or a bundler: require('es5-shim'); // Recommended for comprehensive polyfilling require('es6-shim'); // Now, ES6 features are available globally console.log('--- Map Example ---'); const myMap = new Map(); myMap.set('key1', 'value1'); myMap.set('key2', 'value2'); console.log('Map size:', myMap.size); console.log('Has key1:', myMap.has('key1')); console.log('\n--- Promise Example ---'); new Promise((resolve) => { setTimeout(() => resolve('Promise resolved!'), 100); }).then(message => { console.log(message); }).catch(error => { console.error('Promise rejected:', error); }); console.log('\n--- String.prototype.includes Example ---'); const greeting = 'Hello world!'; console.log('"world" included:', greeting.includes('world')); console.log('"foo" included:', greeting.includes('foo')); console.log('\n--- Number.isInteger Example ---'); console.log('Is 42 an integer:', Number.isInteger(42)); console.log('Is 3.14 an integer:', Number.isInteger(3.14));

Debug

Known issues

breakingThe `Reflect.enumerate` shim was removed from `es6-shim` in version 0.35.0, aligning with its removal from the official ECMAScript specification.

fix

Refactor any code relying on `Reflect.enumerate` to use alternative introspection methods, or if absolutely necessary, stick to an `es6-shim` version prior to 0.35.0. However, relying on a removed spec feature is not recommended.

affects: >=0.35.0

gotchaFor comprehensive and correct polyfilling, `es5-shim` must always be loaded *before* `es6-shim`. Some ES6 features (like `Map` and `Set`) rely on correct ES5 property descriptor behavior, which `es5-shim` corrects in older environments.

fix

In browsers, ensure `<script src="es5-shim.js">` appears before `<script src="es6-shim.js">`. In CommonJS, `require('es5-shim');` must precede `require('es6-shim');`.

affects: all

gotchaThe `Map` and `Set` shims, among others, require the target JavaScript environment to have support for ES5 property descriptors. Without this, these shims may not function correctly or at all.

fix

Always include `es5-shim` alongside `es6-shim`, as `es5-shim` provides the necessary polyfills for ES5 property descriptor support in older environments.

affects: all

gotchaThe `String.prototype.normalize` shim is incomplete by itself and requires the separate `unorm` package to provide the underlying Unicode normalization algorithm.

fix

If `String.prototype.normalize` is needed, install `unorm` (`npm install unorm`) and ensure it's loaded alongside `es6-shim` (e.g., `require('unorm');`).

affects: all

gotchaThe `es6-shim` package provides two main files: `es6-shim.js` (for generally safe shims) and `es6-sham.js` (for shims that are less compliant or have potential side effects, such as `Function.prototype.name`).

fix

If you require shims for features covered by `es6-sham.js`, you must explicitly include it (e.g., `require('es6-shim/es6-sham');`) *after* `es6-shim.js`.

affects: all

Errors

Common errors & fixes

TypeError: 'Map' is not a constructor (or similar for Set, Promise)

The `es6-shim` was not loaded, or `es5-shim` (a prerequisite for some features) was not loaded, or the browser/environment is too old even for shims.

fix

Ensure `es5-shim` and `es6-shim` are correctly loaded in the specified order before attempting to use ES6 features. Verify that the browser/environment meets the minimum requirements for the shims to function.

Uncaught (in promise) TypeError: A promise was rejected with a non-error object. (or similar 'uncaught rejection' console warnings)

Older Chrome versions (pre-50) or certain environments might incorrectly handle promise rejections, particularly with non-Error objects, leading to console warnings or errors.

fix

Update `es6-shim` to version 0.34.3 or higher, which includes fixes for these issues. Additionally, ensure all promises have a `.catch()` handler to explicitly manage rejections and prevent unhandled promise rejections.

ReferenceError: Promise is not defined (or Map, Set, etc. is not defined)

The `es6-shim` was not loaded at all, or not loaded early enough in the execution flow before these global objects were accessed.

fix

Verify that the `es6-shim` script is included in your HTML before your application code, or that `require('es6-shim')` is called at the very top of your application's entry point or module where these features are first used.

SyntaxError: 'const' is a reserved word (or similar for `let`, arrow functions)

`es6-shim` polyfills ECMAScript 6 *features* (e.g., `Map`, `Promise`), but it does not transpile ECMAScript 6+ *syntax* (`const`, `let`, arrow functions, classes) for older JavaScript engines.

fix

For environments that do not support modern JavaScript syntax, you must use a transpiler like Babel to convert ES6+ syntax to ES5-compatible code. `es6-shim` only provides runtime polyfills for built-in objects and methods.

Upgrade

Version history

0.35.8latest on npm

Audit

Dependencies

es5-shimrequiredRequired to correct broken ES5 implementations and should be loaded before `es6-shim` for comprehensive polyfilling. Some ES6 features (like Map/Set) rely on ES5 property descriptor support.

unormoptionalOptional dependency required only if `String.prototype.normalize` support is needed, as it provides the underlying Unicode normalization algorithm.

Agent activity

4 hits · last 30 days

node

Resources

githubhttps://github.com/paulmillr/es6-shim ↗

packagehttps://www.npmjs.com/package/es6-shim ↗