writeResult is undefined when trying to replicate example #917
Description
I am using firestore in react.
I am trying to replicate the example documentation.
I am able to set the doc with the value provided but function is returning undefined on being fulfilled.
The below code which is taken from documentation here is returning writeResult is undefined.
I am able to successfully write the doc though.
Can anyone check.
let documentRef = firestore.doc('col/doc');
documentRef.set({foo: 'bar'}).then(writeResult => {
console.log(`Document written at: ${writeResult.writeTime}`);
});