diff --git a/src/core_plugins/kibana/public/dashboard/dashboard_app.js b/src/core_plugins/kibana/public/dashboard/dashboard_app.js
index 58cad9edd5440..e4f1e90163759 100644
--- a/src/core_plugins/kibana/public/dashboard/dashboard_app.js
+++ b/src/core_plugins/kibana/public/dashboard/dashboard_app.js
@@ -46,7 +46,7 @@ import { DashboardSaveModal } from './top_nav/save_modal';
 import { showAddPanel } from './top_nav/show_add_panel';
 import { showOptionsPopover } from './top_nav/show_options_popover';
 import { showShareContextMenu, ShareContextMenuExtensionsRegistryProvider } from 'ui/share';
-import { migrateLegacyQuery } from 'ui/utils/migrateLegacyQuery';
+import { migrateLegacyQuery } from 'ui/utils/migrate_legacy_query';
 import * as filterActions from 'ui/doc_table/actions/filter';
 import { FilterManagerProvider } from 'ui/filter_manager';
 import { EmbeddableFactoriesRegistryProvider } from 'ui/embeddable/embeddable_factories_registry';
diff --git a/src/core_plugins/kibana/public/discover/controllers/discover.js b/src/core_plugins/kibana/public/discover/controllers/discover.js
index e6b6947d07a94..7cae352421c2a 100644
--- a/src/core_plugins/kibana/public/discover/controllers/discover.js
+++ b/src/core_plugins/kibana/public/discover/controllers/discover.js
@@ -46,7 +46,7 @@ import uiRoutes from 'ui/routes';
 import { uiModules } from 'ui/modules';
 import indexTemplate from '../index.html';
 import { StateProvider } from 'ui/state_management/state';
-import { migrateLegacyQuery } from 'ui/utils/migrateLegacyQuery';
+import { migrateLegacyQuery } from 'ui/utils/migrate_legacy_query';
 import { FilterManagerProvider } from 'ui/filter_manager';
 import { SavedObjectsClientProvider } from 'ui/saved_objects';
 import { visualizationLoader } from 'ui/visualize/loader/visualization_loader';
diff --git a/src/core_plugins/kibana/public/visualize/editor/editor.js b/src/core_plugins/kibana/public/visualize/editor/editor.js
index 489391c82705a..45ec9462124a2 100644
--- a/src/core_plugins/kibana/public/visualize/editor/editor.js
+++ b/src/core_plugins/kibana/public/visualize/editor/editor.js
@@ -39,7 +39,7 @@ import { DashboardConstants } from '../../dashboard/dashboard_constants';
 import { VisualizeConstants } from '../visualize_constants';
 import { KibanaParsedUrl } from 'ui/url/kibana_parsed_url';
 import { absoluteToParsedUrl } from 'ui/url/absolute_to_parsed_url';
-import { migrateLegacyQuery } from 'ui/utils/migrateLegacyQuery';
+import { migrateLegacyQuery } from 'ui/utils/migrate_legacy_query';
 import { recentlyAccessed } from 'ui/persisted_log';
 import { timefilter } from 'ui/timefilter';
 import { getVisualizeLoader } from '../../../../../ui/public/visualize/loader';
diff --git a/src/dev/precommit_hook/casing_check_config.js b/src/dev/precommit_hook/casing_check_config.js
index 9ed1c638a6b32..d25e3c571cce3 100644
--- a/src/dev/precommit_hook/casing_check_config.js
+++ b/src/dev/precommit_hook/casing_check_config.js
@@ -185,7 +185,7 @@ export const TEMPORARILY_IGNORED_PATHS = [
   'src/ui/public/styles/variables/bootstrap-mods.less',
   'src/ui/public/styles/variables/for-theme.less',
   'src/ui/public/typeahead/partials/typeahead-items.html',
-  'src/ui/public/utils/migrateLegacyQuery.js',
+  'src/ui/public/utils/migrate_legacy_query.js',
   'test/functional/apps/management/exports/_import_objects-conflicts.json',
   'packages/kbn-ui-framework/doc_site/src/images/elastic-logo.svg',
   'packages/kbn-ui-framework/doc_site/src/images/hint-arrow.svg',
diff --git a/src/ui/public/courier/saved_object/saved_object.js b/src/ui/public/courier/saved_object/saved_object.js
index 26d4b625b8b0b..11fd135b4cf21 100644
--- a/src/ui/public/courier/saved_object/saved_object.js
+++ b/src/ui/public/courier/saved_object/saved_object.js
@@ -36,7 +36,7 @@ import MappingSetupProvider from '../../utils/mapping_setup';
 
 import { SearchSourceProvider } from '../search_source';
 import { SavedObjectsClientProvider, findObjectByTitle } from '../../saved_objects';
-import { migrateLegacyQuery } from '../../utils/migrateLegacyQuery.js';
+import { migrateLegacyQuery } from '../../utils/migrate_legacy_query';
 import { recentlyAccessed } from '../../persisted_log';
 
 /**
diff --git a/src/ui/public/utils/migrateLegacyQuery.js b/src/ui/public/utils/migrate_legacy_query.ts
similarity index 92%
rename from src/ui/public/utils/migrateLegacyQuery.js
rename to src/ui/public/utils/migrate_legacy_query.ts
index 9d09a3159e0a2..4beccb38b2b9d 100644
--- a/src/ui/public/utils/migrateLegacyQuery.js
+++ b/src/ui/public/utils/migrate_legacy_query.ts
@@ -25,11 +25,10 @@ import { has } from 'lodash';
  * @param query - a legacy query, what used to be stored in SearchSource's query property
  * @return Object
  */
-export function migrateLegacyQuery(query) {
-
+export function migrateLegacyQuery(query: object): object {
   // Lucene was the only option before, so language-less queries are all lucene
   if (!has(query, 'language')) {
-    return { query: query, language: 'lucene' };
+    return { query, language: 'lucene' };
   }
 
   return query;
diff --git a/src/ui/public/utils/numeric.js b/src/ui/public/utils/numeric.ts
similarity index 95%
rename from src/ui/public/utils/numeric.js
rename to src/ui/public/utils/numeric.ts
index fefc72687f295..1342498cf5dc3 100644
--- a/src/ui/public/utils/numeric.js
+++ b/src/ui/public/utils/numeric.ts
@@ -19,6 +19,6 @@
 
 import _ from 'lodash';
 
-export function isNumeric(v) {
+export function isNumeric(v: any): boolean {
   return !_.isNaN(v) && (typeof v === 'number' || (!Array.isArray(v) && !_.isNaN(parseFloat(v))));
 }
diff --git a/src/ui/public/utils/sort_prefix_first.js b/src/ui/public/utils/sort_prefix_first.ts
similarity index 85%
rename from src/ui/public/utils/sort_prefix_first.js
rename to src/ui/public/utils/sort_prefix_first.ts
index 4ed30fa21f393..4d1a8d7f39866 100644
--- a/src/ui/public/utils/sort_prefix_first.js
+++ b/src/ui/public/utils/sort_prefix_first.ts
@@ -19,13 +19,15 @@
 
 import { partition } from 'lodash';
 
-export function sortPrefixFirst(array, prefix, property) {
-  if (!prefix) return array;
+export function sortPrefixFirst(array: any[], prefix?: string | number, property?: string): any[] {
+  if (!prefix) {
+    return array;
+  }
   const lowerCasePrefix = ('' + prefix).toLowerCase();
 
   const partitions = partition(array, entry => {
     const value = ('' + (property ? entry[property] : entry)).toLowerCase();
     return value.startsWith(lowerCasePrefix);
   });
-  return [ ...partitions[0], ...partitions[1] ];
+  return [...partitions[0], ...partitions[1]];
 }
diff --git a/src/ui/public/utils/string_utils.js b/src/ui/public/utils/string_utils.ts
similarity index 95%
rename from src/ui/public/utils/string_utils.js
rename to src/ui/public/utils/string_utils.ts
index 9d194b6e89bf1..22a57aeb07933 100644
--- a/src/ui/public/utils/string_utils.js
+++ b/src/ui/public/utils/string_utils.ts
@@ -18,13 +18,12 @@
  */
 
 export class StringUtils {
-
   /**
    * Returns a version of the string with the first letter capitalized.
    * @param str {string}
    * @returns {string}
    */
-  static upperFirst(str) {
+  public static upperFirst(str: string): string {
     return str ? str.charAt(0).toUpperCase() + str.slice(1) : '';
   }
 }