graphql-js是用Vanilla JavaScript编写的吗？

Question

I started to learn graphql-js source code, but found it is difficult to determine whether the source code is written in vanilla js or typescript ?

For example, the main entry file src/graphql.js has the following code:

import type { GraphQLSchema } from './type/schema';
import type { ExecutionResult } from './execution/execute';

I don't think the import type is standard js syntax. Can anyone please help explain what it is for?

Also, the following code looks like TypeScript to me, but the file extension is js , not ts :

function graphql( 
   schema: GraphQLSchema,
   requestString: string,
   rootValue?: mixed,
   contextValue?: mixed,
   variableValues?: ?{[key: string]: mixed},
   operationName?: ?string):: Promise<ExecutionResult> {}

Answer 1

After asking the question, I did some research. Apparently graphql-js uses the Flow Type , which is similar to TypeScript . James Kyles from Babel and Flow team explained the difference between Flow Type and TypeScript very well here