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46 lines
1.6 KiB
46 lines
1.6 KiB
/** |
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* Copyright (c) 2013-present, Facebook, Inc. |
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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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* @providesModule getScrollPosition |
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* @typechecks |
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*/ |
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'use strict'; |
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const getDocumentScrollElement = require('./getDocumentScrollElement'); |
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const getUnboundedScrollPosition = require('./getUnboundedScrollPosition'); |
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/** |
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* Gets the scroll position of the supplied element or window. |
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* |
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* The return values are bounded. This means that if the scroll position is |
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* negative or exceeds the element boundaries (which is possible using inertial |
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* scrolling), you will get zero or the maximum scroll position, respectively. |
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* |
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* If you need the unbound scroll position, use `getUnboundedScrollPosition`. |
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* |
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* @param {DOMWindow|DOMElement} scrollable |
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* @return {object} Map with `x` and `y` keys. |
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*/ |
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function getScrollPosition(scrollable) { |
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const documentScrollElement = getDocumentScrollElement(scrollable.ownerDocument || scrollable.document); |
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if (scrollable.Window && scrollable instanceof scrollable.Window) { |
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scrollable = documentScrollElement; |
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} |
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const scrollPosition = getUnboundedScrollPosition(scrollable); |
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const viewport = scrollable === documentScrollElement ? scrollable.ownerDocument.documentElement : scrollable; |
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const xMax = scrollable.scrollWidth - viewport.clientWidth; |
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const yMax = scrollable.scrollHeight - viewport.clientHeight; |
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scrollPosition.x = Math.max(0, Math.min(scrollPosition.x, xMax)); |
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scrollPosition.y = Math.max(0, Math.min(scrollPosition.y, yMax)); |
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return scrollPosition; |
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} |
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module.exports = getScrollPosition; |