(function() {
  class AnotElement extends HTMLElement {
    constructor() {
      super();
      this.attachShadow({'mode': 'open'});
    }

    listItem() {
      const arr = JSON.parse(window.localStorage.getItem('annotations'));
      return arr?arr:[];
    }

    hasItem(text) {
      return text == '' || this.listItem().filter(stext => text === stext).length > 0;
    }

    saveItem(text) {
      if (!this.hasItem(text)) {
        const arr = this.listItem();
        arr.push(text);
        window.localStorage.setItem('annotations', JSON.stringify(arr));
      }
    }

    delItem(text) {
      const arr = this.listItem().filter(stext => text !== stext);
      localStorage.setItem('annotations', JSON.stringify(arr.length>0?arr:[]));
    }
  }