@servie/events/dist/index.js

Tiny type-safe event emitter

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.once = exports.Emitter = exports.ALL_EVENTS = void 0;
/**
 * All events are emitted using this key.
 */
exports.ALL_EVENTS = Symbol("ALL_EVENTS");
/**
 * Create an `off` function given an input.
 */
function add(stack, value) {
    stack.add(value);
    return function off() {
        return stack.delete(value);
    };
}
/**
 * Emit an event.
 */
function emit(stack, ...args) {
    if (stack)
        for (const { fn } of stack)
            fn(...args);
}
/**
 * Type-safe event emitter.
 */
class Emitter {
    constructor() {
        this.$ = Object.create(null);
    }
    on(type, fn) {
        const stack = (this.$[type] = this.$[type] || new Set());
        return add(stack, { fn });
    }
    emit(type, ...args) {
        emit(this.$[type], ...args);
        emit(this.$[exports.ALL_EVENTS], { type, args });
    }
}
exports.Emitter = Emitter;
/**
 * Helper to listen to an event once only.
 */
function once(events, type, callback) {
    const off = events.on(type, function once(...args) {
        off();
        return callback(...args);
    });
    return off;
}
exports.once = once;
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