50 lines
1.1 KiB
Plaintext
50 lines
1.1 KiB
Plaintext
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/**
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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 keyMirror
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* @typechecks static-only
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* @flow
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*/
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'use strict';
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var invariant = require("./invariant");
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/**
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* Constructs an enumeration with keys equal to their value.
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*
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* For example:
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*
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* var COLORS = keyMirror({blue: null, red: null});
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* var myColor = COLORS.blue;
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* var isColorValid = !!COLORS[myColor];
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*
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* The last line could not be performed if the values of the generated enum were
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* not equal to their keys.
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*
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* Input: {key1: val1, key2: val2}
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* Output: {key1: key1, key2: key2}
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*
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* @param {object} obj
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* @return {object}
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*/
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var keyMirror = function <T: {}>(obj: T): $ObjMapi<T, <K>(K) => K> {
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var ret = {};
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var key;
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invariant(obj instanceof Object && !Array.isArray(obj), 'keyMirror(...): Argument must be an object.');
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for (key in obj) {
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if (!obj.hasOwnProperty(key)) {
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continue;
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}
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ret[key] = key;
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}
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return ret;
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};
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module.exports = keyMirror;
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