Methods for tying the return type of a function to its arguments

Tie Return Type of a Function to its Arguments.ts

// The return type matches the type of argument provided
const doSomething = <T>(data: T) : T[] => {
    // processing...
    return result; // array of type T
}

const something = doSomething(1) // type number[]


// For more complex narrowing...

// Interface maps a key to a certain type
interface TweetMap {
    text: TextTweet,
    media: MediaTweet,
}

const getTweetsByType = <T extends keyof TweetMap>(
    type: T
): TweetMap[T][] => {
    // processing...
    return result; // Return type is tied to argument provided
}

const textTweets = getTweetsByType('text') // textTweets is now of type TextTweet[]