Is there a way to incorporate new members into a pre-existing type in TypeScript?

While examining the definition file for the commander project, one can observe the following interface being utilized:

interface IExportedCommand extends ICommand {
    Command: commander.ICommandStatic;
    Option: commander.IOptionStatic;
    [key: string]: any;
}

The generic [key: string]: any; is useful, but I am interested in potentially enhancing this by specifying named members within my own files.

Unfortunately, due to the namespacing and module behavior (which I still feel slightly unsure about), I have been unable to find the correct method.

I believe that through declaration merging, there may be a way for me to extend this interface with additional members. However, it's also possible that it is not achievable and I haven't been able to confirm that yet...

typescript

Answer №1

To include this functionality in your code, you can simply add the following lines:

interface IExportedCommand {
    myOption: string;
}

If you plan to use this interface across multiple files, it's advisable to store it in a separate file. If your IDE doesn't automatically recognize it, you can force recognition by including a reference comment in the header of your file.

/// <reference path="path/to/your/file.ts" />

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