es5-shim: A JavaScript repository from ValeryVS

#es5-shim

es5-shim.js and es5-shim.min.js monkey-patch a JavaScript context to contain all EcmaScript 5 methods that can be faithfully emulated with a legacy JavaScript engine. Note: As es5-shim.js is designed to patch the native Javascript engine, it should be the library that is loaded first.

es5-sham.js and es5-sham.min.js monkey-patch other ES5 methods as closely as possible. For these methods, as closely as possible to ES5 is not very close. Many of these shams are intended only to allow code to be written to ES5 without causing run-time errors in older engines. In many cases, this means that these shams cause many ES5 methods to silently fail. Decide carefully whether this is what you want. Note: es5-sham.js requires es5-shim.js to be able to work properly.

Tests

The tests are written with the Jasmine BDD test framework. To run the tests, navigate to /tests/ , or, simply npm install and npm test.

Shims

Complete tests

Array.prototype.every
Array.prototype.filter
Array.prototype.forEach
Array.prototype.indexOf
Array.prototype.lastIndexOf
Array.prototype.map
Array.prototype.slice
Array.prototype.some
Array.prototype.sort
Array.prototype.reduce
Array.prototype.reduceRight
Array.prototype.push
Array.prototype.join
Array.isArray
Date.now
Date.prototype.toJSON
Function.prototype.bind
- ⚠️ Caveat: the bound function has a prototype property.
- ⚠️ Caveat: bound functions do not try too hard to keep you from manipulating their arguments and caller properties.
- ⚠️ Caveat: bound functions don't have checks in call and apply to avoid executing as a constructor.
Number.prototype.toFixed
Number.prototype.toPrecision
Object.keys
String.prototype.split
String.prototype.trim
String.prototype.lastIndexOf
String.prototype.replace
- Firefox (through v29) natively handles capturing groups incorrectly.
Date.parse (for ISO parsing)
Date.prototype.toISOString
parseInt
parseFloat
Error.prototype.toString
Error.prototype.name
Error.prototype.message
RegExp.prototype.toString

Shams

⚠️ Object.create

For the case of simply "begetting" an object that inherits prototypically from another, this should work fine across legacy engines.

⚠️ The second argument is passed to Object.defineProperties which will probably fail either silently or with extreme prejudice.
⚠️ Object.getPrototypeOf

This will return "undefined" in some cases. It uses __proto__ if it's available. Failing that, it uses constructor.prototype, which depends on the constructor property of the object's prototype having not been replaced. If your object was created like this, it won't work:
```
  function Foo() {
  }
  Foo.prototype = {};
```
Because the prototype reassignment destroys the constructor property.

This will work for all objects that were created using Object.create implemented with this library.
⚠️ Object.getOwnPropertyNames

This method uses Object.keys, so it will not be accurate on legacy engines.
Object.isSealed

Returns "false" in all legacy engines for all objects, which is conveniently guaranteed to be accurate.
Object.isFrozen

Returns "false" in all legacy engines for all objects, which is conveniently guaranteed to be accurate.
Object.isExtensible

Works like a charm, by trying very hard to extend the object then redacting the extension.

May fail

⚠️ Object.getOwnPropertyDescriptor

The behavior of this shim does not conform to ES5. It should probably not be used at this time, until its behavior has been reviewed and been confirmed to be useful in legacy engines.
⚠️ Object.defineProperty

In the worst of circumstances, IE 8 provides a version of this method that only works on DOM objects. This sham will not be installed. The given version of defineProperty will throw an exception if used on non-DOM objects.

In slightly better circumstances, this method will silently fail to set "writable", "enumerable", and "configurable" properties.

Providing a getter or setter with "get" or "set" on a descriptor will silently fail on engines that lack "defineGetter" and "defineSetter", which include all versions of IE.

https://github.com/es-shims/es5-shim/issues#issue/5
⚠️ Object.defineProperties

This uses the Object.defineProperty shim.
Object.seal

Silently fails on all legacy engines. This should be fine unless you are depending on the safety and security provisions of this method, which you cannot possibly obtain in legacy engines.
Object.freeze

Silently fails on all legacy engines. This should be fine unless you are depending on the safety and security provisions of this method, which you cannot possibly obtain in legacy engines.
Object.preventExtensions

Silently fails on all legacy engines. This should be fine unless you are depending on the safety and security provisions of this method, which you cannot possibly obtain in legacy engines.

Example of applying ES compatability shims in a browser project