code: function Field(elem) {
        this.selector = elem.selector;
        $elem = this.$elem = $(elem.selector);
        this.name = elem.name;
  
        this.top = $elem.offset().top;
        this.height = $elem.height();
        this.bottom = this.top + this.height;
        this.width = $elem.width();
      }
docs: /*
  Constructors