Javascript | Sprites animator

JS - Sprites animator.js

animated_sprite = function () {
    this.vars = {
        currentIndex : 0,
        path         : null,
        class        : null,
        interval     : null,
        lenght       : null,
        time         : null
    }
    this.init = function(sprite, lenght = null, time)
    {
        this.vars.paths = document.querySelector("." + sprite);
        this.vars.class = sprite;
        this.vars.lenght = lenght;
        this.vars.time = time;
        window.clearInterval(this.vars.interval);
        this.vars.interval = window.setInterval(this.draw_image.bind(this), this.vars.time);
    }
    this.draw_image = function ()
    {
        this.vars.paths.setAttribute('class', this.vars.class + ' ' + this.vars.class + '_' + this.vars.currentIndex);

        if (this.vars.currentIndex < this.vars.lenght - 1) {
            this.vars.currentIndex += 1;
        } else {
            this.vars.currentIndex = 0;
        }
    }
    this.stop = function ()
    {
        window.clearInterval(this.vars.interval);
    },
    this.play = function ()
    {
        this.vars.interval = window.setInterval(this.draw_image.bind(this), this.vars.time);    
    }
};