How to use the localforage.getItems function in localforage

return (dispatch) => {
			// Announce gene request from cache/server,
			// add genes to fetchingGenes to indicate
			// they are being fetched
			dispatch(requestGenesFetch(unfetched, path, title));

			let cacheKeys = new Array(unfetched.length);
			for (let i = 0; i < unfetched.length; i++) {
				cacheKeys[i] = path + '/' + unfetched[i];
			}
			// try loading from cache
			localforage.getItems(cacheKeys)
				// store all genes retrieved from cache
				.then((retrievedGenes) => {
					let cachedNames = [],
						cachedGenes = {},
						keys = Object.keys(retrievedGenes) ;
					for (let i = 0; i < keys.length; i++) {
						let gene = retrievedGenes[keys[i]];
						// each key that is uncached returns as an
						// undefined entry in this array
						if (gene) {
							cachedGenes[gene.name] = gene;
							cachedNames.push(gene.name);
						}
					}
					if (cachedNames.length) {
						// the overlapping names are the cached names

componentDidMount = () => {
    if (
      this.slateEditor &&
      this.slateEditor.value &&
      !this.slateEditor.state.value.hasUndos
    ) {
      /**
       * Finds all used image keys in the document.
       * @const contentImageKeys
       */
      const contentImageKeys = this.slateEditor.value
        .toJSON()
        .document.nodes.filter(node => !!(node.data && node.data.key))
        .map(node => node.data.key)

      localForage.getItems().then(storedImageKeys => {
        /**
         * Creates a list of image keys in the database which aren't part of the content.
         * @var unusedImageKeys
         */
        let unusedImageKeys = []
        Object.keys(storedImageKeys).forEach(storedKey => {
          let unused = true
          contentImageKeys.forEach(usedKey => {
            if (storedKey === usedKey) {
              unused = false
            }
          })
          unused && unusedImageKeys.push(storedKey)
        })
        unusedImageKeys.forEach(imageKey => {
          localForage.removeItem(imageKey)