Error: Error in parsing: ... Line 212: Unexpected token => while doing gulp serve

Question

Facing an issue while using =>

incomingDemandCodes.findIndex(record => record.a === b[0].a);

in place of

incomingDemandCodes.findIndex(function (record){
  return  record.a === b[0].a;
});

where b & incomingDemandCodes are the arrays a as one property.

and the error that I receive during the Gulp serve is

internal/streams/legacy.js:59
  throw er; // Unhandled stream error in pipe.
  ^

Error: Error in parsing: "bay-status\editDemand-dialog.controller.js", Line 212: Unexpected token =>