# es-shims/es5-shim

ECMAScript 5 compatibility shims for legacy (and modern) JavaScript engines

Repository: https://github.com/es-shims/es5-shim
Canonical: https://ross.abutalabs.com/products/es5-shim
Language: JavaScript
License: MIT
License Family: permissive
Topics: shim, polyfill, ecmascript, javascript, es5
Last push: 2025-12-30T01:54:28+00:00

## Health v2 (maintenance only)
Score: 49/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 59, release rhythm 8, longevity 100
- inputs: {"age_days": 5830, "days_push": 247, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 7077, forks 876 (observed 2026-08-28T04:09:55.726094+00:00)

## What it is
es5-shim is a JavaScript library that monkey-patches legacy JavaScript engines to provide ECMAScript 5 methods that can be faithfully emulated, with a companion es5-sham for methods that can only be approximated. It lets developers write ES5 code that runs in older engines like legacy browsers.

## Use cases
- support ES5 array methods like map, filter, and forEach in old browsers
- run modern JavaScript code in legacy engines like IE8
- polyfill Function.prototype.bind and Date.now in old environments
- make ES5 code run without runtime errors on outdated JavaScript engines
- add ECMAScript 5 compatibility to a legacy web project

## When to choose
- you must support legacy browsers or engines lacking ES5 features
- you want a well-tested, comprehensive ES5 polyfill loaded before other scripts
- you need per-method standalone shims for targeted patching

## When to avoid
- your target environments already support ES5 natively
- you need ES6+ features like promises, arrow functions, or classes
- you cannot tolerate the partial or silently-failing behavior of es5-sham methods

## Facets
- artifact type: library
- maturity: maintenance
- function: developer-tools
- domain: web-development, developer-tools
- platform: browser, cross-platform
- tags: polyfill, shim, es5, ecmascript, javascript, legacy-browser-support, nodejs

## Member repositories
- es-shims/es5-shim (main) score 49

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:09:55.726094+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-29T17:40:12.417189+00:00, confidence not recorded.
  - readme: https://github.com/es-shims/es5-shim (fetched 2026-08-28T04:09:55.726094+00:00, sha e79c3b9beefb)
  - registry_npm: https://registry.npmjs.org/es5-shim (fetched 2026-08-29T08:36:16.429062+00:00, sha 0841f96949c2)
- Data as of 2026-08-30T08:39:29.467469+00:00.