Can't get async to work in react-native

Question

I am trying to run the following code block from the official react-native docs :

  async function getMoviesFromApi() {
    try {
      let response = await fetch('https://facebook.github.io/react-native/movies.json');
      let responseJson = await response.json();
      return responseJson.movies;
    } catch(error) {
      console.error(error);
    }
  }

When I try running this I get the error:

"Unexpected token, expected ( (31:17)"

If I remove the function keyword, it works fine.

What difference does it make if I use the function keyword or not? Is it because I am using it in a class? Where in the documentation does it indicate this? Is it in the react-native documentation or the JavaScript documentation? I cannot seem to find it either place, though I could be searching for the wrong thing.

I am using react-native: 0.38.0 (with react-native-cli: 1.2.0)

Answer 1

Is it because I am using it in a class?

Probably. The syntax for declaring methods in a class is

class Foo {
  method() {}
}

not

class Foo {
  function method() {}
}

Hence an async method is declared as

class Foo {
  async method() {}
}

Where in the documentation does it indicate this? Is it in the react-native documentation or the JavaScript documentation?

It's JavaScript. React is a framework/library, not a language. All the syntax you are using is JavaScript (except JSX of course, but that's not specific to React either).

See the MDN documentation about classe s.