"__extends" function repeats multiple times inside compiled code.

[logashoff]

The following piece of code is being included into each compiled module whenever a class is extended inside that module:

var __extends = (this && this.__extends) || function (d, b) {
    for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
    function __() { this.constructor = d; }
    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
};

So if you have 10 modules that have a class in each one of them that extends some other class, you'll have 10 exactly the same __extends functions in your compiled code.

[smrq]

That's just how the TS compiler works. Deduplicating that code is way, way outside the scope of this project.

I suppose it's possible that some sort of clever minifier could deal with it, but it would be quite tricky.

[logashoff]

Is it possible to put all TypeScript boilerplate code above compiled modules? Maybe wrap everything in a function so it doesn't become part of the global scope.

Is this issue part of tsify functionality or should it be handled by some other 3rd party post-processor?

[smrq]

The problem is that TypeScript compiles each file as its own separate chunk, including the boilerplate in each one. It would be untenable to try and detect what's boilerplate vs. what's not on a per-file basis.

Post-processing might work... I sure wouldn't want to try and maintain it, though. Better would be a TS compiler feature to do some sort of boilerplate extraction.

Either way, definitely not going to happen at this level. It's too far removed from what this package does. It's not a bad idea, though.

[logashoff]

Pull-request regarding this issue has already been merged: microsoft/TypeScript#2901

There is --noEmitHelpers compiler flag which won't generate __extends function, but it can be included separately.