200 lines
8.3 KiB
Markdown
200 lines
8.3 KiB
Markdown
# es5-shim <sup>[![Version Badge][npm-version-svg]][package-url]</sup>
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[![github actions][actions-image]][actions-url]
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[![coverage][codecov-image]][codecov-url]
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[![dependency status][deps-svg]][deps-url]
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[![dev dependency status][dev-deps-svg]][dev-deps-url]
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[![License][license-image]][license-url]
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[![Downloads][downloads-image]][downloads-url]
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[![npm badge][npm-badge-png]][package-url]
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`es5-shim.js` and `es5-shim.min.js` monkey-patch a JavaScript context to
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contain all EcmaScript 5 methods that can be faithfully emulated with a
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legacy JavaScript engine.
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**Note:** As `es5-shim.js` is designed to patch the native Javascript
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engine, it should be the library that is loaded first.
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`es5-sham.js` and `es5-sham.min.js` monkey-patch other ES5 methods as
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closely as possible. For these methods, as closely as possible to ES5
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is not very close. Many of these shams are intended only to allow code
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to be written to ES5 without causing run-time errors in older engines.
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In many cases, this means that these shams cause many ES5 methods to
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silently fail. Decide carefully whether this is what you want.
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**Note:** `es5-sham.js` requires `es5-shim.js` to be able to work properly.
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## Tests
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The tests are written with the Jasmine BDD test framework.
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To run the tests, navigate to <root-folder>/tests/ , or,
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simply `npm install` and `npm test`.
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## Shims
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### Complete tests ###
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* Array.prototype.every ([standalone shim](https://www.npmjs.com/package/array.prototype.every))
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* Array.prototype.filter ([standalone shim](https://www.npmjs.com/package/array.prototype.filter))
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* Array.prototype.forEach ([standalone shim](https://www.npmjs.com/package/array.prototype.foreach))
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* Array.prototype.indexOf ([standalone shim](https://www.npmjs.com/package/array.prototype.indexof))
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* Array.prototype.lastIndexOf ([standalone shim](https://www.npmjs.com/package/array.prototype.lastindexof))
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* Array.prototype.map ([standalone shim](https://www.npmjs.com/package/array.prototype.map))
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* Array.prototype.slice
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* Array.prototype.some ([standalone shim](https://www.npmjs.com/package/array.prototype.some))
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* Array.prototype.sort
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* Array.prototype.reduce ([standalone shim](https://www.npmjs.com/package/array.prototype.reduce))
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* Array.prototype.reduceRight ([standalone shim](https://www.npmjs.com/package/array.prototype.reduceright))
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* Array.prototype.push ([standalone shim](https://www.npmjs.com/package/array.prototype.push))
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* Array.prototype.join
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* Array.prototype.splice ([standalone shim](https://www.npmjs.com/package/array.prototype.splice))
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* Array.isArray
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* Date.now
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* Date.prototype.toJSON
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* Function.prototype.bind
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* :warning: Caveat: the bound function has a prototype property.
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* :warning: Caveat: bound functions do not try too hard to keep you
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from manipulating their ``arguments`` and ``caller`` properties.
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* :warning: Caveat: bound functions don't have checks in ``call`` and
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``apply`` to avoid executing as a constructor.
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* Number.prototype.toExponential ([standalone shim](https://www.npmjs.com/package/number.prototype.toexponential))
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* Number.prototype.toFixed
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* Number.prototype.toPrecision
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* Object.keys ([standalone shim](https://www.npmjs.com/package/object-keys))
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* String.prototype.split ([standalone shim](https://www.npmjs.com/package/string.prototype.split))
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* String.prototype.trim ([standalone shim](https://www.npmjs.com/package/string.prototype.trim))
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* String.prototype.lastIndexOf ([standalone shim](https://string.prototype.lastindexof))
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* String.prototype.replace
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* Firefox (through v29) natively handles capturing groups incorrectly.
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* Date.parse (for ISO parsing)
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* Date.prototype.toISOString
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* parseInt
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* parseFloat
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* Error.prototype.toString
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* Error.prototype.name
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* Error.prototype.message
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* RegExp.prototype.toString
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## Shams
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* :warning: Object.create
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For the case of simply "begetting" an object that inherits
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prototypically from another, this should work fine across legacy
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engines.
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:warning: The second argument is passed to Object.defineProperties
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which will probably fail either silently or with extreme prejudice.
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* :warning: Object.getPrototypeOf
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This will return "undefined" in some cases. It uses `__proto__` if
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it's available. Failing that, it uses constructor.prototype, which
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depends on the constructor property of the object's prototype having
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not been replaced. If your object was created like this, it won't
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work:
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function Foo() {
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}
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Foo.prototype = {};
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Because the prototype reassignment destroys the constructor
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property.
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This will work for all objects that were created using
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`Object.create` implemented with this library.
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* :warning: Object.getOwnPropertyNames
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This method uses Object.keys, so it will not be accurate on legacy
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engines.
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* Object.isSealed
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Returns "false" in all legacy engines for all objects, which is
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conveniently guaranteed to be accurate.
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* Object.isFrozen
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Returns "false" in all legacy engines for all objects, which is
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conveniently guaranteed to be accurate.
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* Object.isExtensible
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Works like a charm, by trying very hard to extend the object then
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redacting the extension.
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### May fail
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* :warning: Object.getOwnPropertyDescriptor
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The behavior of this shim does not conform to ES5. It should
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probably not be used at this time, until its behavior has been
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reviewed and been confirmed to be useful in legacy engines.
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* :warning: Object.defineProperty
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In the worst of circumstances, IE 8 provides a version of this
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method that only works on DOM objects. This sham will not be
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installed. The given version of `defineProperty` will throw an
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exception if used on non-DOM objects.
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In slightly better circumstances, this method will silently fail to
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set "writable", "enumerable", and "configurable" properties.
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Providing a getter or setter with "get" or "set" on a descriptor
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will silently fail on engines that lack "__defineGetter__" and
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"__defineSetter__", which include all versions of IE.
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https://github.com/es-shims/es5-shim/issues#issue/5
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* :warning: Object.defineProperties
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This uses the Object.defineProperty shim.
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* Object.seal
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Silently fails on all legacy engines. This should be
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fine unless you are depending on the safety and security
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provisions of this method, which you cannot possibly
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obtain in legacy engines.
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* Object.freeze
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Silently fails on all legacy engines. This should be
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fine unless you are depending on the safety and security
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provisions of this method, which you cannot possibly
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obtain in legacy engines.
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* Object.preventExtensions
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Silently fails on all legacy engines. This should be
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fine unless you are depending on the safety and security
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provisions of this method, which you cannot possibly
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obtain in legacy engines.
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### Example of applying ES compatibility shims in a browser project
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```html
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<script src="https://cdnjs.cloudflare.com/ajax/libs/es5-shim/4.5.14/es5-shim.min.js"></script>
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<script src="https://cdnjs.cloudflare.com/ajax/libs/es5-shim/4.5.14/es5-sham.min.js"></script>
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<script src="https://cdnjs.cloudflare.com/ajax/libs/json3/3.3.2/json3.min.js"></script>
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<script src="https://cdnjs.cloudflare.com/ajax/libs/es6-shim/0.35.5/es6-shim.min.js"></script>
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<script src="https://cdnjs.cloudflare.com/ajax/libs/es6-shim/0.35.5/es6-sham.min.js"></script>
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<script src="other-libs.js"></script>
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```
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[package-url]: https://npmjs.org/package/es5-shim
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[npm-version-svg]: https://versionbadg.es/es-shims/es5-shim.svg
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[deps-svg]: https://david-dm.org/es-shims/es5-shim.svg
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[deps-url]: https://david-dm.org/es-shims/es5-shim
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[dev-deps-svg]: https://david-dm.org/es-shims/es5-shim/dev-status.svg
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[dev-deps-url]: https://david-dm.org/es-shims/es5-shim#info=devDependencies
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[npm-badge-png]: https://nodei.co/npm/es5-shim.png?downloads=true&stars=true
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[license-image]: https://img.shields.io/npm/l/es5-shim.svg
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[license-url]: LICENSE
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[downloads-image]: https://img.shields.io/npm/dm/es5-shim.svg
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[downloads-url]: https://npm-stat.com/charts.html?package=es5-shim
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[codecov-image]: https://codecov.io/gh/es-shims/es5-shim/branch/main/graphs/badge.svg
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[codecov-url]: https://app.codecov.io/gh/es-shims/es5-shim/
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[actions-image]: https://img.shields.io/endpoint?url=https://github-actions-badge-u3jn4tfpocch.runkit.sh/es-shims/es5-shim
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[actions-url]: https://github.com/es-shims/es5-shim/actions
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