TypeScript 5.8 Ships --erasableSyntaxOnly To Disable Enums
TypeScript 5.8's new erasableSyntaxOnly flag enforces pure type annotations by disabling enums, namespaces, and parameter properties.
In TypeScript, if you try to assign to a property of a possibly undefined object, you'll get an error:
'X' is possibly undefined.
obj .foo = "bar";'obj' is possibly 'undefined'.18048'obj' is possibly 'undefined'.
You might think that you can use the optional chaining syntax to fix this:
obj ?. foo = "bar";The left-hand side of an assignment expression may not be an optional property access.2779The left-hand side of an assignment expression may not be an optional property access.
But you end up with an error:
The left-hand side of an assignment expression may not be an optional property access.
This is because optional chaining is only for reading properties (or deleting properties), not for assigning to them.
But today, the optional chaining for assignments proposal has landed in Stage 1 of TC39.
If this proposal gets adopted into JavaScript, the code below will no longer error.
obj ?. foo = "bar";The left-hand side of an assignment expression may not be an optional property access.2779The left-hand side of an assignment expression may not be an optional property access.
Optional Chaining for Assignments Lands in Stage 1
TypeScript 5.8's new erasableSyntaxOnly flag enforces pure type annotations by disabling enums, namespaces, and parameter properties.
TypeScript is coming to Node 23. Let's break down what that means.
Learn how to extract the type of an array element in TypeScript using the powerful Array[number]
trick.
Learn how to publish a package to npm with a complete setup including, TypeScript, Prettier, Vitest, GitHub Actions, and versioning with Changesets.
Enums in TypeScript can be confusing, with differences between numeric and string enums causing unexpected behaviors.
Is TypeScript just a linter? No, but yes.