Mastering TypeScript 3 - Third Edition

await messages

The final topic we will discuss on async await is how to process messages that are returned within our promises. Consider the following promise definition:

function asyncWithMessage() : Promise<string> { 
    return new Promise<string> ( 
        (             resolve: (message: string ) => void, 
            reject: (message: string) => void 
        ) => { 
            function afterWait() { 
                resolve("resolve_message"); 
            } 
            setTimeout(afterWait, 1000); 
        } 
    ); 
} 

Here, we have defined a standard function returning a promise after a 1 second delay. The code to note here is the call to resolve within the afterWait function that is sending a message back to the callback. In this case, it is returning a string value of resolve_message, which matches our Promise<string> syntax. Again, we can ...