add pickDeep utility function to pick nested properties from objects

test/common/libs/pickDeep.js

@@ -0,0 +1,34 @@
+import pickDeep from '../../../common/script/libs/pickDeep';
+
+describe('pickDeep', () => {
+  it('throws an error if "properties" is not an array', () => {
+    expect(pickDeep).to.throw(Error);
+  });
+
+  it('returns an object of properties taken from the input object', () => {
+    let obj = {
+      a: true,
+      b: [1, 2, 3],
+      c: {
+        nested: {
+          two: {
+            times: true,
+          },
+        },
+      },
+      d: false,
+    };
+
+    let res = pickDeep(obj, ['a', 'b[0]', 'c.nested.two.times']);
+    expect(res.a).to.be.true;
+    expect(res.b).to.eql([1]);
+    expect(res.c).to.eql({
+      nested: {
+        two: {
+          times: true,
+        },
+      },
+    });
+    expect(res).to.not.have.property('d');
+  });
+});