1 | import { map as higherOrderMap } from 'rxjs/operators';
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2 | import { Observable } from 'rxjs';
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3 |
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4 | /**
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5 | * Applies a given `project` function to each value emitted by the source
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6 | * Observable, and emits the resulting values as an Observable.
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7 | *
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8 | * <span class="informal">Like [Array.prototype.map()](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map),
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9 | * it passes each source value through a transformation function to get
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10 | * corresponding output values.</span>
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11 | *
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12 | * <img src="./img/map.png" width="100%">
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13 | *
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14 | * Similar to the well known `Array.prototype.map` function, this operator
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15 | * applies a projection to each value and emits that projection in the output
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16 | * Observable.
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17 | *
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18 | * @example <caption>Map every click to the clientX position of that click</caption>
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19 | * var clicks = Rx.Observable.fromEvent(document, 'click');
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20 | * var positions = clicks.map(ev => ev.clientX);
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21 | * positions.subscribe(x => console.log(x));
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22 | *
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23 | * @see {@link mapTo}
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24 | * @see {@link pluck}
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25 | *
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26 | * @param {function(value: T, index: number): R} project The function to apply
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27 | * to each `value` emitted by the source Observable. The `index` parameter is
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28 | * the number `i` for the i-th emission that has happened since the
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29 | * subscription, starting from the number `0`.
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30 | * @param {any} [thisArg] An optional argument to define what `this` is in the
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31 | * `project` function.
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32 | * @return {Observable<R>} An Observable that emits the values from the source
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33 | * Observable transformed by the given `project` function.
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34 | * @method map
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35 | * @owner Observable
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36 | */
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37 | export function map<T, R>(this: Observable<T>, project: (value: T, index: number) => R, thisArg?: any): Observable<R> {
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38 | return higherOrderMap(project, thisArg)(this);
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39 | }
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