Migrate to TS: rename .js to .ts and fix everything in latter PRs (graphql#3088)

using this `find src -name "*.js" -exec sh -c 'git mv "$0" "${0%.js}.ts"' {} \;` shell command renamed all files in `src`

Author: saihaj

src/jsutils/ObjMap.js

@@ -1 +1 @@
-export type PromiseOrValue<T> = Promise<T> | T;
+export type PromiseOrValue<+T> = Promise<T> | T;

src/jsutils/PromiseOrValue.ts

@@ -2,8 +2,12 @@
  * Returns true if the provided object implements the AsyncIterator protocol via
  * implementing a `Symbol.asyncIterator` method.
  */
-export function isAsyncIterable(
-  maybeAsyncIterable: any,
-): maybeAsyncIterable is AsyncIterable<unknown> {
+declare function isAsyncIterable(
+  value: mixed,
+  // $FlowFixMe[invalid-in-rhs]
+): boolean %checks(value instanceof AsyncIterable);
+
+// eslint-disable-next-line no-redeclare
+export function isAsyncIterable(maybeAsyncIterable) {
   return typeof maybeAsyncIterable?.[Symbol.asyncIterator] === 'function';
 }

src/jsutils/isAsyncIterable.ts

@@ -2,6 +2,10 @@
  * Returns true if the value acts like a Promise, i.e. has a "then" function,
  * otherwise returns false.
  */
-export function isPromise(value: any): value is Promise<unknown> {
+declare function isPromise(value: mixed): boolean %checks(value instanceof
+  Promise);
+
+// eslint-disable-next-line no-redeclare
+export function isPromise(value) {
   return typeof value?.then === 'function';
 }