If you don't control the original definition file, and can't make adjustments to it, then unfortunately, what you're trying to do isn't supported currently in TypeScript. An interface
in TypeScript is the only construct that allows reasonable extensions as it is only a compile-time/syntax check and not a run-time operation.
You cannot extend a class
in TypeScript with new functionality using only TypeScript (and expecting code-completion/Intellisense to work as expected). You could of course add the functions to the prototype
for the CircleMarker
class, but they would be unavailable to Intellisense and would fail to compile unless you use a type assertion.
Instead of using any
, you should be able to use an interface
with the type assertion:
declare module L {
export interface CircleMarkerEx {
bindLabel(name: string, options: any): CircleMarker;
}
}
Then:
var cm = <L.CircleMakerEx> circle.bindLabel("name", {});
Thankfully, it doesn't add any run-time overhead, just a bit of extra typing (pun intended!).
There have been suggestions for things like "mix-ins" on CodePlex, but they have not been implemented. Even the mix-in suggestions would not be entirely straightforward to use, and wouldn't work well for libraries that weren't entirely written in TypeScript (as it would be too easy to have JavaScript code that simply could not be safely constructed for example with a mix-in).