add selector for canvas label and id

__tests__/src/selectors/index.test.js

@@ -13,6 +13,7 @@ import {
   getThumbnailNavigationPosition,
   getManifestTitle,
   getWindowViewType,
+  getIdAndLabelOfCanvases,
 } from '../../../src/state/selectors';
 
 
@@ -254,3 +255,29 @@ describe('getDestructuredMetadata', () => {
     expect(received).toEqual([]);
   });
 });
+
+describe('getIdAndLabelOfCanvases', () => {
+  it('should return id and label of each canvas in manifest', () => {
+    const canvases = manifesto
+      .create(manifestFixture019)
+      .getSequences()[0]
+      .getCanvases();
+    const received = getIdAndLabelOfCanvases(canvases);
+    const expected = [
+      {
+        id: 'http://iiif.io/api/presentation/2.0/example/fixtures/canvas/24/c1.json',
+        label: 'Test 19 Canvas: 1',
+      },
+      {
+        id: 'https://purl.stanford.edu/fr426cg9537/iiif/canvas/fr426cg9537_1',
+        label: 'Image 1',
+      },
+    ];
+    expect(received).toEqual(expected);
+  });
+
+  it('should return empty array if canvas if empty', () => {
+    const received = getIdAndLabelOfCanvases([]);
+    expect(received).toEqual([]);
+  });
+});

src/state/selectors/index.js

@@ -34,6 +34,18 @@ export function getManifestCanvases(manifest) {
   return manifest.manifestation.getSequences()[0].getCanvases();
 }
 
+/**
+* Return ids and labels of canvases
+* @ param {Array} canvases
+* @return {Array} - [ {id: 'id', label: 'label' }, ... ]
+*/
+export function getIdAndLabelOfCanvases(canvases) {
+  return canvases.map(canvas => ({
+    id: canvas.__jsonld['@id'], // eslint-disable-line no-underscore-dangle
+    label: canvas.__jsonld.label, // eslint-disable-line no-underscore-dangle
+  }));
+}
+
 /**
 * Return the current canvas selected in a window
 * @param {object} state