diff --git a/src/legacy/core_plugins/data/public/index_patterns/index_patterns/flatten_hit.js b/src/legacy/core_plugins/data/public/index_patterns/index_patterns/flatten_hit.ts
similarity index 80%
rename from src/legacy/core_plugins/data/public/index_patterns/index_patterns/flatten_hit.js
rename to src/legacy/core_plugins/data/public/index_patterns/index_patterns/flatten_hit.ts
index b9d25dc0ccb41c..b10c0dca857ff1 100644
--- a/src/legacy/core_plugins/data/public/index_patterns/index_patterns/flatten_hit.js
+++ b/src/legacy/core_plugins/data/public/index_patterns/index_patterns/flatten_hit.ts
@@ -18,18 +18,19 @@
  */
 
 import _ from 'lodash';
+import { IndexPattern } from './';
 
 // Takes a hit, merges it with any stored/scripted fields, and with the metaFields
 // returns a flattened version
 
-function flattenHit(indexPattern, hit, deep) {
-  const flat = {};
+function flattenHit(indexPattern: IndexPattern, hit: Record<string, any>, deep: boolean) {
+  const flat = {} as Record<string, any>;
 
   // recursively merge _source
   const fields = indexPattern.fields.byName;
-  (function flatten(obj, keyPrefix) {
+  (function flatten(obj, keyPrefix = '') {
     keyPrefix = keyPrefix ? keyPrefix + '.' : '';
-    _.forOwn(obj, function (val, key) {
+    _.forOwn(obj, function(val, key) {
       key = keyPrefix + key;
 
       if (deep) {
@@ -52,28 +53,28 @@ function flattenHit(indexPattern, hit, deep) {
         } else if (Array.isArray(flat[key])) {
           flat[key].push(val);
         } else {
-          flat[key] = [ flat[key], val ];
+          flat[key] = [flat[key], val];
         }
         return;
       }
 
       flatten(val, key);
     });
-  }(hit._source));
+  })(hit._source);
 
   return flat;
 }
 
-function decorateFlattenedWrapper(hit, metaFields) {
-  return function (flattened) {
+function decorateFlattenedWrapper(hit: Record<string, any>, metaFields: Record<string, any>) {
+  return function(flattened: Record<string, any>) {
     // assign the meta fields
-    _.each(metaFields, function (meta) {
+    _.each(metaFields, function(meta) {
       if (meta === '_source') return;
       flattened[meta] = hit[meta];
     });
 
     // unwrap computed fields
-    _.forOwn(hit.fields, function (val, key) {
+    _.forOwn(hit.fields, function(val, key: any) {
       if (key[0] === '_' && !_.contains(metaFields, key)) return;
       flattened[key] = Array.isArray(val) && val.length === 1 ? val[0] : val;
     });
@@ -88,8 +89,12 @@ function decorateFlattenedWrapper(hit, metaFields) {
  *
  * @internal
  */
-export function flattenHitWrapper(indexPattern, metaFields = {}, cache = new WeakMap()) {
-  return function cachedFlatten(hit, deep = false) {
+export function flattenHitWrapper(
+  indexPattern: IndexPattern,
+  metaFields = {},
+  cache = new WeakMap()
+) {
+  return function cachedFlatten(hit: Record<string, any>, deep = false) {
     const decorateFlattened = decorateFlattenedWrapper(hit, metaFields);
     const cached = cache.get(hit);
     const flattened = cached || flattenHit(indexPattern, hit, deep);
diff --git a/src/legacy/core_plugins/data/public/index_patterns/index_patterns/index.ts b/src/legacy/core_plugins/data/public/index_patterns/index_patterns/index.ts
index 31ff03d51f97a6..4ca7e053a4492f 100644
--- a/src/legacy/core_plugins/data/public/index_patterns/index_patterns/index.ts
+++ b/src/legacy/core_plugins/data/public/index_patterns/index_patterns/index.ts
@@ -17,7 +17,6 @@
  * under the License.
  */
 
-// @ts-ignore
 export * from './flatten_hit';
 export * from './format_hit';
 export * from './index_pattern';
diff --git a/src/legacy/core_plugins/data/public/index_patterns/index_patterns/index_pattern.tsx b/src/legacy/core_plugins/data/public/index_patterns/index_patterns/index_pattern.tsx
index fe8cf2442db087..ec1005bdce2610 100644
--- a/src/legacy/core_plugins/data/public/index_patterns/index_patterns/index_pattern.tsx
+++ b/src/legacy/core_plugins/data/public/index_patterns/index_patterns/index_pattern.tsx
@@ -38,7 +38,6 @@ import { Field, FieldList, FieldType } from '../fields';
 import { createFieldsFetcher } from './_fields_fetcher';
 import { getRoutes } from '../utils';
 import { formatHitProvider } from './format_hit';
-// @ts-ignore
 import { flattenHitWrapper } from './flatten_hit';
 import { IndexPatternsApiClient } from './index_patterns_api_client';
 
diff --git a/src/legacy/core_plugins/data/public/index_patterns/index_patterns_service.mock.ts b/src/legacy/core_plugins/data/public/index_patterns/index_patterns_service.mock.ts
index d4e5cc011d5f3b..5dcf4005ef4e86 100644
--- a/src/legacy/core_plugins/data/public/index_patterns/index_patterns_service.mock.ts
+++ b/src/legacy/core_plugins/data/public/index_patterns/index_patterns_service.mock.ts
@@ -18,8 +18,7 @@
  */
 
 import { IndexPatternsService, IndexPatternsSetup } from '.';
-// @ts-ignore
-import { flattenHitWrapper } from './index_patterns/flatten_hit';
+import { flattenHitWrapper } from './index_patterns';
 
 type IndexPatternsServiceClientContract = PublicMethodsOf<IndexPatternsService>;
 
diff --git a/src/legacy/core_plugins/data/public/index_patterns/index_patterns_service.ts b/src/legacy/core_plugins/data/public/index_patterns/index_patterns_service.ts
index 8ecca8fa94a142..5f8a66f733c42e 100644
--- a/src/legacy/core_plugins/data/public/index_patterns/index_patterns_service.ts
+++ b/src/legacy/core_plugins/data/public/index_patterns/index_patterns_service.ts
@@ -19,8 +19,7 @@
 
 import { UiSettingsClientContract, SavedObjectsClientContract } from 'src/core/public';
 import { Field, FieldList, FieldType } from './fields';
-// @ts-ignore
-import { createFlattenHitWrapper } from './index_patterns/flatten_hit';
+import { createFlattenHitWrapper } from './index_patterns';
 import { createIndexPatternSelect } from './components';
 import {
   formatHitProvider,
diff --git a/src/legacy/core_plugins/kbn_doc_views/public/views/table/table.test.tsx b/src/legacy/core_plugins/kbn_doc_views/public/views/table/table.test.tsx
index 03437e7b1ac261..d70402af83345a 100644
--- a/src/legacy/core_plugins/kbn_doc_views/public/views/table/table.test.tsx
+++ b/src/legacy/core_plugins/kbn_doc_views/public/views/table/table.test.tsx
@@ -21,7 +21,6 @@ import { mount } from 'enzyme';
 import { IndexPattern } from 'ui/index_patterns';
 // @ts-ignore
 import { findTestSubject } from '@elastic/eui/lib/test';
-// @ts-ignore
 import { flattenHitWrapper } from '../../../../data/public/index_patterns/index_patterns/flatten_hit';
 import { DocViewTable } from './table';