Rendering HTML from map function in React Context API render function

Question

I'm trying to render out a list of titles by calling map on state from inside the <MyContext.Consumer> component but the code is not returning the list items. However, if I do a console.log(dataImTryingToMap); it shows exactly what I'm trying to render. The <ul> is rendered but no <li> 's are. There are no errors thrown by create-react-app. What am I missing??? Here is the consumer component:

<MyContext.Consumer>
    {context => (
        <ul>
            {Object.keys(context.state.subjects).map(subject => {
                <li>{context.state.subjects[subject].title}</li>;
                console.log(context.state.subjects[subject].title);
             })}
        </ul>
    )}
</MyContext.Consumer>

The console log returns exactly the data I'm looking for, but nothing shows on the screen.

And here is the state from the <MyContext.MyProvider> component:

state = {
    subjects: {
        subject0: {
            title: "Math",
            description: "",
            cards: {
                card1: {
                    note: "",
                    answer: ""
                }
            }
        },
        subject1: {
            title: "history",
            description: "",
            cards: {
                card1: {
                    note: "",
                    answer: ""
                }
            }
        }
    }
};

Thanks for any help!

Answer 1

You are not returning anything from the Array.map() callback:

{Object.keys(context.state.subjects).map(subject => {
    <li>{context.state.subjects[subject].title}</li>; <-- this is not returned
    console.log(context.state.subjects[subject].title);
 })}

 const contextValue = { state: {"subjects":{"subject0":{"title":"Math","description":"","cards":{"card1":{"note":"","answer":""}}},"subject1":{"title":"history","description":"","cards":{"card1":{"note":"","answer":""}}}}}}; const MyContext = React.createContext(); const Example = () => ( <MyContext.Consumer> {context => ( <ul> {Object.keys(context.state.subjects).map(subject => { console.log(context.state.subjects[subject].title); return ( <li key={subject}>{context.state.subjects[subject].title}</li> ); })} </ul> )} </MyContext.Consumer> ); const Demo = ({ value }) => ( <MyContext.Provider value={value}> <Example /> </MyContext.Provider> ); ReactDOM.render( <Demo value={contextValue} />, demo ); 

 <script crossorigin src="https://unpkg.com/react@16.3/umd/react.development.js"></script> <script crossorigin src="https://unpkg.com/react-dom@16.3/umd/react-dom.development.js"></script> <div id="demo"> </demo> 

Answer 2

You haven't returned anything from inside the map function and hence it doesn't render anything. Either return it explicitly like

<MyContext.Consumer>
    {context => (
        <ul>
            {Object.keys(context.state.subjects).map(subject => {
                return <li>{context.state.subjects[subject].title}</li>;
             })}
        </ul>
    )}
</MyContext.Consumer>

or implicitly like

<MyContext.Consumer>
    {context => (
        <ul>
            {Object.keys(context.state.subjects).map(subject => (
                 <li>{context.state.subjects[subject].title}</li>;
            ))}
        </ul>
    )}
</MyContext.Consumer>