sub-events/ext/from-event.js

Lightweight, strongly-typed events, with monitored subscriptions.

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.fromEvent = fromEvent;
var src_1 = require("../dist/src");
/**
 * Creates a strongly-typed, named DOM Event wrapper.
 */
function fromEvent(target, event, options) {
    var sec = new src_1.SubEventCount();
    var handler = function (e) { return sec.emit(e, options); };
    sec.onCount.subscribe(function (info) {
        var start = info.prevCount === 0; // fresh start
        var stop = info.newCount === 0; // no subscriptions left
        if (start) {
            target.addEventListener(event, handler);
        }
        else {
            if (stop) {
                target.removeEventListener(event, handler);
            }
        }
    });
    return sec;
}