image preloader es6

//There are a lot of image preloaders out there
// This one is supposed to be forgiving
// depends on Emmitter https://github.com/JFusco/es6-event-emitter

class Preloader extends Emitter {

    constructor(pathList, options) {
        super();
        this.defaults = {
            prefix: null
        };
        _.extend(this.defaults, options);

        this.pathList = pathList;
        this.loadedImages = [];
        this.total = this.pathList.length;
        this.counter = 0;
        this.percent = 0;

        this.loadImages();
    }

    //overides
    // each(count, percent) {}
    // done(imageList) {}

    loadImages() {
        let self = this;
        for (var i = 0; i < this.pathList.length; i++) {
            try {
                var img = this.loadedImages[i] = document.createElement('img');
                if (this.defaults.prefix) {
                    //add trailing slash if doesn't exists
                    var prefix = this.defaults.prefix.replace(/\/?$/, '/');
                }
                else {
                    prefix = '';
                }

                img.onload = ()=> {
                    this.counter++;
                    this.percent = (this.counter / this.total) * 100;

                    this.trigger('each', this.counter, this.percent);
                    if (this.counter === this.total) {
                        this.trigger('done', this.loadedImages);
                    }
                };

                img.onerror = (err)=> {
                    //prevent component from stoping if last image is not found
                    this.counter++;
                    if (this.total === this.counter) {
                        this.trigger('each', this.counter, 100);
                        this.trigger('done', this.loadedImages);
                    }
                };
                img.src = prefix + this.pathList[i];
            } catch (err) {
                console.warn(err);
            }

        }
    }
}

// example usage
let preloader = new Preloader(list, {
    prefix: 'static/images'
});
preloader.on('each', (count, percent) => {
    console.log(count, percent);
});
preloader.on('done', (rsp) => {
    console.log(rsp);
});