more functional jQuery

jquery-set-class.js

$.fn.extend({
  setClass: function(name, add) {
    if(typeof name === 'object') {
      const classes = name;
      Object.keys(classes).forEach(className => {
        this.setClass(className, classes[className]);
      });
    } else {
      this.each((index, elem) => {
        if(add) {
          $(elem).addClass(name);
        } else {
          $(elem).removeClass(name);
        }
      });
    }
    return this;
  }
});