ix/asynciterable/fromeventpattern.js

The Interactive Extensions for JavaScript

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.fromEventPattern = void 0;
const tslib_1 = require("tslib");
const memoize_js_1 = require("./operators/memoize.js");
const identity_js_1 = require("../util/identity.js");
const isiterable_js_1 = require("../util/isiterable.js");
const asyncsink_js_1 = require("./asyncsink.js");
const { isArray } = Array;
function callOrApply(fn, args) {
    return isArray(args) ? fn(...args) : fn(args);
}
/**
 * Creates async-iterable from an event emitter by adding handlers for both listening and unsubscribing from events.
 *
 * @template TSource The type of elements in the event emitter.
 * @param {(handler: (...args: any[]) => void) => void} addHandler The function to add a listener to the source.
 * @param {(handler: (...args: any[]) => void) => void} removeHandler The function to remove a listener from the source.
 * @returns {AsyncIterableX<TSource>} An async-iterable which contains the data from the underlying events as wrapped by the handlers.
 */
function fromEventPattern(addHandler, removeHandler, resultSelector) {
    if (!(0, isiterable_js_1.isFunction)(resultSelector)) {
        resultSelector = identity_js_1.identity;
    }
    const sink = new asyncsink_js_1.AsyncSink();
    const handler = (...args) => sink.write(callOrApply(resultSelector, args));
    addHandler(handler);
    const loop = function () {
        return tslib_1.__asyncGenerator(this, arguments, function* () {
            try {
                for (let next; !(next = yield tslib_1.__await(sink.next())).done;) {
                    yield yield tslib_1.__await(next.value);
                }
            }
            finally {
                removeHandler(handler);
                sink.end();
            }
        });
    };
    return (0, memoize_js_1.memoize)()(loop());
}
exports.fromEventPattern = fromEventPattern;

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