Are We Saying Goodbye to Enums?

TypeScript 5.8 is here, and it brings some big changes! The two main updates are Granular Checks for Branches in Return Expressions and the new --erasableSyntaxOnly flag. These changes help us write safer and cleaner code, and we might also be in very first stages of saying goodbye to enums!

TypeScript 5.8 is here, and it brings some big changes!

TypeScript Trusted Us Too Much

Before TypeScript 5.8, return values in some conditional statements weren’t always checked properly. This could lead to weird bugs that only show up in runtime.

This code for example:

declare const untypedCache: Map<any, any>;

function getUrlObject(urlString: string): URL {
    return untypedCache.has(urlString) ?
        untypedCache.get(urlString) :
        urlString;
}

As mentioned in docs, when TypeScript checks conditional expressions like cond ? trueBranch : falseBranch, its type is treated as a union of the types of the two branches.

In above code, untypedCache.has(urlString) going to be any and urlString having a string type, and union of those going to be any and as we all know, any can be a crazy witch!

Now, TypeScript handle this, checking both branches of the return statement. If one part returns something unexpected, it will do the complain!

The…