[META] - Converted makeId to TS + tests (#1759)

* [Pagination] - Updated Changelog

* Code Review - Moved Changelog entry to current master

* [META] - Converted  to TS + tests

* Updated Changelog

* Added Non-null assertion operator before graphicColors

* [META] - Converted  to TS + tests

* Updated Changelog

* Code review fixes

CHANGELOG.md

@@ -1,5 +1,6 @@
 ## [`master`](https://github.com/elastic/eui/tree/master)
 
+- Converted `makeId` to TS ([#1759](https://github.com/elastic/eui/pull/1759))
 - Converted `EuiCardGraphic` to TS ([#1751](https://github.com/elastic/eui/pull/1751))
 - Enhanced the build process to emit TypeScript types for the variables extracted from the themes ([#1750](https://github.com/elastic/eui/pull/1750))
 

src/components/form/form_row/index.d.ts

@@ -6,7 +6,6 @@ declare module '@elastic/eui' {
   /**
    * @see './form_row.js'
    */
-
   export type EuiFormRowCommonProps = CommonProps & {
     error?: ReactNode | ReactNode[];
     fullWidth?: boolean;

src/components/form/form_row/make_id.test.ts

@@ -0,0 +1,21 @@
+import makeId from './make_id';
+
+describe('makeId', () => {
+  let ids: Map<string, boolean>;
+  beforeEach(() => {
+    ids = new Map<string, boolean>();
+  });
+
+  test('returns a string of length 8', () => {
+    expect(makeId()).toHaveLength(8);
+  });
+
+  // Could be slow so adding a [SLOW] tag for use with --testNamePattern=<regex>
+  test('returns a random string - [SLOW]', () => {
+    for (let i = 0; i < 60000; i += 1) {
+      const id: string = makeId();
+      expect(ids.has(id)).toBeFalsy();
+      ids.set(id, true);
+    }
+  });
+});

src/components/form/form_row/make_id.js → src/components/form/form_row/make_id.ts

@@ -1,5 +1,9 @@
 // Generate statistically almost-certainly-unique `id`s for associating form
 // inputs with their labels and other descriptive text elements.
-export default function makeId() {
-  return Math.random().toString(36).slice(-8);
+function makeId(): string {
+  return Math.random()
+    .toString(36)
+    .slice(-8);
 }
+
+export default makeId;