undux/dist.esm/emitter.js

Dead simple state management for React

import { Observable } from 'rxjs-observable';
const ALL = '__ALL__';
const CYCLE_ERROR_MESSAGE = '[undux] Error: Cyclical dependency detected. ' +
    'This may cause a stack overflow unless you fix it. \n' +
    'The culprit is the following sequence of .set calls, ' +
    'called from one or more of your Undux Effects: ';
export class Emitter {
    constructor(isDevMode = false) {
        this.isDevMode = isDevMode;
        this.state = {
            callChain: new Set(),
            observables: new Map(),
            observers: new Map(),
        };
    }
    /**
     * Emit an event (silently fails if no listeners are hooked up yet)
     */
    emit(key, value) {
        if (this.isDevMode) {
            if (this.state.callChain.has(key)) {
                console.error(CYCLE_ERROR_MESSAGE +
                    Array.from(this.state.callChain).concat(key).join(' -> '));
                return this;
            }
            else {
                this.state.callChain.add(key);
            }
        }
        if (this.hasChannel(key)) {
            this.emitOnChannel(key, value);
        }
        if (this.hasChannel(ALL)) {
            this.emitOnChannel(ALL, value);
        }
        if (this.isDevMode)
            this.state.callChain.clear();
        return this;
    }
    /**
     * Subscribe to an event
     */
    on(key) {
        return this.createChannel(key);
    }
    /**
     * Subscribe to all events
     */
    all() {
        return this.createChannel(ALL);
    }
    /// private
    createChannel(key) {
        if (!this.state.observers.has(key)) {
            this.state.observers.set(key, []);
        }
        if (!this.state.observables.has(key)) {
            this.state.observables.set(key, []);
        }
        const observable = new Observable((_) => {
            this.state.observers.get(key).push(_);
            return () => this.deleteChannel(key, observable);
        });
        this.state.observables.get(key).push(observable);
        return observable;
    }
    deleteChannel(key, observable) {
        if (!this.state.observables.has(key)) {
            return;
        }
        const array = this.state.observables.get(key);
        const index = array.indexOf(observable);
        if (index < 0) {
            return;
        }
        array.splice(index, 1);
        if (!array.length) {
            this.state.observables.delete(key);
            this.state.observers.delete(key);
        }
    }
    emitOnChannel(key, value) {
        this.state.observers.get(key).forEach((_) => _.next(value));
    }
    hasChannel(key) {
        return this.state.observables.has(key);
    }
}
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