code: function disabled(val) {
    // return whether the first element in the set
    // is hidden
    if(val === undefined) {
      return this.hasClass(className);
    // hide on truthy
    }else if(val) {
      this.addClass(className);
    // show on falsey
    }else{
      this.removeClass(className);
    }
    return this;
  }
docs: Toggles the disabled class on an element.
  
  A typical css rule might be:
  
  .disabled{pointer-events: none; opacity: 0.8;}