42 lines
2.3 KiB
Markdown
42 lines
2.3 KiB
Markdown
# Caveats
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In order for certain features to work they require certain polyfills. You can
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satisfy **all** 6to5 feature requirements by using the included
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[polyfill](polyfill.md). You may alternatively selectively include what you need:
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| Feature | Requirements |
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| --------------------------- | ---------------------------------------------------------------------------------------------------------------------------- |
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| Abstract References | [experimental](usage.md#experimental), `Symbol` |
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| Array destructuring | `Array.isArray`, `Array.from` |
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| Async functions, Generators | [experimental](usage.md#experimental), [regenerator runtime](https://github.com/facebook/regenerator/blob/master/runtime.js) |
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| Comprehensions | [experimental](usage.md#experimental), `Array.isArray`, `Array.from` |
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| For Of | `Symbol`, `prototype[Symbol.iterator]` |
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| Object spread/rest | [experimental](usage.md#experimental), `Object.assign` |
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| Spread | `Array.isArray`, `Array.from` |
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## Classes
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Built-in classes such as `Date`, `Array` and `DOM` cannot be subclassed due to
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limitations in ES5 implementations.
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If you're inheriting from a class then static properties are inherited from it
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via [\_\_proto\_\_](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/proto),
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this is widely supported but you may run into problems with much older browsers.
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**NOTE:** `__proto__` is not supported on IE <= 9 so static properties
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**will not** be inherited. A possible workaround is to use `super();`:
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```javascript
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class Foo {
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static foo() {
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}
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}
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class Bar extends Foo {
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static foo() {
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super();
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}
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}
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```
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