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a0733fe13d
* pure A higher-order component version of the `React.PureComponent` class. During an update, the previous props are compared to the new props. If they are the same, React will skip rendering the component and its children. Unlike userspace implementations, `pure` will not add an additional fiber to the tree. The first argument must be a functional component; it does not work with classes. `pure` uses shallow comparison by default, like `React.PureComponent`. A custom comparison can be passed as the second argument. Co-authored-by: Andrew Clark <acdlite@fb.com> Co-authored-by: Sophie Alpert <sophiebits@fb.com> * Warn if first argument is not a functional component
61 lines
1.9 KiB
JavaScript
61 lines
1.9 KiB
JavaScript
/**
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*
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* @flow
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*/
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// The Symbol used to tag the ReactElement-like types. If there is no native Symbol
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// nor polyfill, then a plain number is used for performance.
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const hasSymbol = typeof Symbol === 'function' && Symbol.for;
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export const REACT_ELEMENT_TYPE = hasSymbol
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? Symbol.for('react.element')
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: 0xeac7;
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export const REACT_PORTAL_TYPE = hasSymbol
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? Symbol.for('react.portal')
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: 0xeaca;
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export const REACT_FRAGMENT_TYPE = hasSymbol
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? Symbol.for('react.fragment')
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: 0xeacb;
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export const REACT_STRICT_MODE_TYPE = hasSymbol
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? Symbol.for('react.strict_mode')
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: 0xeacc;
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export const REACT_PROFILER_TYPE = hasSymbol
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? Symbol.for('react.profiler')
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: 0xead2;
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export const REACT_PROVIDER_TYPE = hasSymbol
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? Symbol.for('react.provider')
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: 0xeacd;
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export const REACT_CONTEXT_TYPE = hasSymbol
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? Symbol.for('react.context')
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: 0xeace;
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export const REACT_CONCURRENT_MODE_TYPE = hasSymbol
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? Symbol.for('react.concurrent_mode')
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: 0xeacf;
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export const REACT_FORWARD_REF_TYPE = hasSymbol
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? Symbol.for('react.forward_ref')
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: 0xead0;
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export const REACT_PLACEHOLDER_TYPE = hasSymbol
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? Symbol.for('react.placeholder')
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: 0xead1;
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export const REACT_PURE_TYPE = hasSymbol ? Symbol.for('react.pure') : 0xead3;
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const MAYBE_ITERATOR_SYMBOL = typeof Symbol === 'function' && Symbol.iterator;
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const FAUX_ITERATOR_SYMBOL = '@@iterator';
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export function getIteratorFn(maybeIterable: ?any): ?() => ?Iterator<*> {
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if (maybeIterable === null || typeof maybeIterable !== 'object') {
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return null;
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}
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const maybeIterator =
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(MAYBE_ITERATOR_SYMBOL && maybeIterable[MAYBE_ITERATOR_SYMBOL]) ||
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maybeIterable[FAUX_ITERATOR_SYMBOL];
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if (typeof maybeIterator === 'function') {
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return maybeIterator;
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}
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return null;
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}
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