Add period.

Typescript Type -> TypeScript type

Please change globally from Typescript to TypeScript.

Done

Start a new sentence. How about:

If this looks familiar, it's because that's also how you reference the _____ variable in TypeScript.

Please be sure to specify the variable (sometimes a word like "that" can be vague).

Done

How about (or something like - we just need to streamline it and state exactly what we are doing):

To access the hero data the ______ returns, use dot notation to traverse the mutationResult and assign it to a _____.

I don't know the exact words that should go in the blanks.

done.

Once you have access to the data, push them into the heroes array.

We want a complete sentence here.

Done.

That

This class initializes a schema property in the constructor.

Done.

How about this:

Next, the query function takes as an argument the request, or query, and executes that query using the GraphQL execute function against the schema property.

Took almost as is but changed a small thing. let me know if that makes sense

This:

You send empty objects to the rootValue and contextValue arguments of the function

Loses me. I get the second part of the sentence about variables and operationName but where is the first part happening in the code? It may be as simple as saying:

You send empty objects to the rootValue and contextValue arguments of the function with X and Y respectively.

X and Y being code snippets like {} or whatever is actually doing it.

ohh I thought that empty objects are enough.
Ok changed the whole sentence, let me know what you think

Now -> Lastly

This lets them know we are at the end of covering what's happening in this code snippet.

Done

Let's save the details about the conclusion for when we have finalized everything. Then we can make sure it has everything in the same way we are planning for the table of contents.

API, and

Done

I've been thinking about this one for a while but only just now came up with this:

GraphQL is a replacement or enhancement for REST and can be used in conjunction with it.

Much better! done.

to

Done.

your server -> the server

Done.

Please search for and update spec -> specification and docs -> documentation.

done.

Type -> type

Done.

object. --> object:

It seems like it would flow better with a semicolon.

Done.

Once --> "Now that..."

Done.

mutate --> mutate

(Please put in code font).

Done.

At this point

also

Now your existing heroes app can add a hero using GraphQL.

Done.

Since these first three sentences start with "GraphQL", could we vary the language a little? Maybe one could start with "The GraphQL..." <--- I don't know what the right word would be there. In regular language, interface would work, but considering the context, we can't use that, right? Another way we could reduce repetition in the language could be by combining two of these sentences.

Maybe the first and third could be combined with the third starting with "It" instead. Then we leave the subsection immediately after.

done

, helping your Angular app: --> "that helps your Angular app do the following:"

done

that --> "three key points" or "these key points"

We want intros to lists to be complete sentences, rather than having the list items complete the sentence. I just recently came to understand that if you're wondering why I hadn't mentioned it before.

done

comma before or

done

Please remove one of the occurrences of "multiple" since they are close together. Does that still work? Is there another word we could use for the second one? Maybe "various"?

done

This is the first mention of the Apollo Client. We should add a phrase explaining in just a few words (to preserve brevity) what the Apollo Client is:

"....the Apollo Client, the x that lets you x, what data...."

or:
"....the Apollo Client, covered later,...."

done

"And then modify" --> "and then modify".

done

the problem here is that --> but as your app grows

done

please put a comma after and

done

This is helpful, but we can't rely on third party for the download. We should change this to the live example/downloadable example of the TOH.

done