once(name, listener) {
        const doOnce = function () {
            listener.apply(null, arguments);
            this.removeListener(name, doOnce);
        }.bind(this);
        this.on(name, doOnce);
        return this;
    }
/**
    Registers a listener on the emitter that only executes once
    @method EventEmitter#once
    @param {String} name - The name of the event
    @param {Function} listener - The callback function
    @return {EventEmitter} - Returns a reference to the `EventEmitter` so that calls can be chained
    **/
Registers a listener on the emitter that only executes once
Registers a listener on the emitter that only executes once
once(name, listener) {
        const doOnce = function () {
            listener.apply(null, arguments);
            this.removeListener(name, doOnce);
        }.bind(this);
        this.on(name, doOnce);
        return this;
    }
once ( name , listener ) { const doOnce = function ( ) { listener . apply ( null , arguments ) ; this . removeListener ( name , doOnce ) ; } . bind ( this ) ; this . on ( name , doOnce ) ; return this ; }
Registers a listener on the emitter that only executes once
Registers a listener on the emitter that only executes once