grapick/src/emitter.js

Easy configurable gradient picker, with no dependencies

export default class EventEmitter {
    on(name, callback, ctx) {
      var e = this.e || (this.e = {});

      (e[name] || (e[name] = [])).push({
        fn: callback,
        ctx: ctx
      });

      return this;
    }

    once(name, callback, ctx) {
      var self = this;
      function listener () {
        self.off(name, listener);
        callback.apply(ctx, arguments);
      };

      listener._ = callback
      return this.on(name, listener, ctx);
    }

    emit(name) {
      var data = [].slice.call(arguments, 1);
      var evtArr = ((this.e || (this.e = {}))[name] || []).slice();
      var i = 0;
      var len = evtArr.length;

      for (i; i < len; i++) {
        evtArr[i].fn.apply(evtArr[i].ctx, data);
      }

      return this;
    }

    off(name, callback) {
      var e = this.e || (this.e = {});
      var evts = e[name];
      var liveEvents = [];

      if (evts && callback) {
        for (var i = 0, len = evts.length; i < len; i++) {
          if (evts[i].fn !== callback && evts[i].fn._ !== callback)
            liveEvents.push(evts[i]);
        }
      }

      // Remove event from queue to prevent memory leak
      // Suggested by https://github.com/lazd
      // Ref: https://github.com/scottcorgan/tiny-emitter/commit/c6ebfaa9bc973b33d110a84a307742b7cf94c953#commitcomment-5024910

      (liveEvents.length)
        ? e[name] = liveEvents
        : delete e[name];

      return this;
    }
}