grpc-js: Use helper isFunction

Author: zereraz

packages/grpc-js/src/client.ts

@@ -55,6 +55,10 @@ const INTERCEPTOR_SYMBOL = Symbol();
 const INTERCEPTOR_PROVIDER_SYMBOL = Symbol();
 const CALL_INVOCATION_TRANSFORMER_SYMBOL = Symbol();
 
+function isFunction<ResponseType>(arg: Metadata | CallOptions | UnaryCallback<ResponseType>): boolean {
+ return Object.prototype.toString.call(arg) === '[object Function]'
+}
+
 export interface UnaryCallback<ResponseType> {
  (err: ServiceError | null, value?: ResponseType): void;
 }
@@ -198,9 +202,9 @@ export class Client {
  options: CallOptions;
  callback: UnaryCallback<ResponseType>;
  } {
- if (Object.prototype.toString.call(arg1) === '[object Function]') {
+ if (isFunction(arg1)) {
  return { metadata: new Metadata(), options: {}, callback: arg1 };
- } else if (Object.prototype.toString.call(arg2) === '[object Function]') {
+ } else if (isFunction(arg2)) {
  if (arg1 instanceof Metadata) {
  return { metadata: arg1, options: {}, callback: arg2 };
  } else {
@@ -211,7 +215,7 @@ export class Client {
  !(
  arg1 instanceof Metadata &&
  arg2 instanceof Object &&
- Object.prototype.toString.call(arg3) === '[object Function]'
+ isFunction(arg3)
  )
  ) {
  throw new Error('Incorrect arguments passed');
@@ -671,3 +675,4 @@ export class Client {
  return stream;
  }
 }
+