77 lines
3.0 KiB
JavaScript
77 lines
3.0 KiB
JavaScript
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"use strict";
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var __extends = (this && this.__extends) || function (d, b) {
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for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
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function __() { this.constructor = d; }
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d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
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};
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var Subscriber_1 = require('../Subscriber');
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/**
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* Returns an Observable that applies a specified accumulator function to the first item emitted by a source Observable,
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* then feeds the result of that function along with the second item emitted by the source Observable into the same
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* function, and so on until all items have been emitted by the source Observable, and emits the final result from
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* the final call to your function as its sole item.
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* This technique, which is called "reduce" here, is sometimes called "aggregate," "fold," "accumulate," "compress," or
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* "inject" in other programming contexts.
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*
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* <img src="./img/reduce.png" width="100%">
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*
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* @param {initialValue} the initial (seed) accumulator value
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* @param {accumulator} an accumulator function to be invoked on each item emitted by the source Observable, the
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* result of which will be used in the next accumulator call.
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* @returns {Observable} an Observable that emits a single item that is the result of accumulating the output from the
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* items emitted by the source Observable.
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*/
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function reduce(project, seed) {
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return this.lift(new ReduceOperator(project, seed));
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}
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exports.reduce = reduce;
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var ReduceOperator = (function () {
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function ReduceOperator(project, seed) {
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this.project = project;
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this.seed = seed;
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}
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ReduceOperator.prototype.call = function (subscriber) {
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return new ReduceSubscriber(subscriber, this.project, this.seed);
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};
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return ReduceOperator;
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}());
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exports.ReduceOperator = ReduceOperator;
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var ReduceSubscriber = (function (_super) {
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__extends(ReduceSubscriber, _super);
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function ReduceSubscriber(destination, project, seed) {
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_super.call(this, destination);
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this.hasValue = false;
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this.acc = seed;
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this.project = project;
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this.hasSeed = typeof seed !== 'undefined';
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}
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ReduceSubscriber.prototype._next = function (value) {
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if (this.hasValue || (this.hasValue = this.hasSeed)) {
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this._tryReduce(value);
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}
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else {
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this.acc = value;
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this.hasValue = true;
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}
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};
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ReduceSubscriber.prototype._tryReduce = function (value) {
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var result;
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try {
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result = this.project(this.acc, value);
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}
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catch (err) {
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this.destination.error(err);
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return;
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}
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this.acc = result;
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};
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ReduceSubscriber.prototype._complete = function () {
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if (this.hasValue || this.hasSeed) {
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this.destination.next(this.acc);
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}
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this.destination.complete();
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};
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return ReduceSubscriber;
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}(Subscriber_1.Subscriber));
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exports.ReduceSubscriber = ReduceSubscriber;
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//# sourceMappingURL=reduce.js.map
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