How to call the method of a JS object from duktape/C?

I thought this should be a simple one but to my surprise I cannot figure out the proper way. Calling a function/method with duktape/C is easy via duk_pcall/duk_pcall_method. The tricky part is how to get to the function to call?

I have a global var process and want to call it’s emit() method. I can simply evaluate the string:

process.emit("exit", code)

and that works nicely. But how to do that in duktape/C? This is what I tried:

  duk_get_global_string(ctx, "process");
  duk_get_prop_string(ctx, -1, "emit");
  duk_push_string(ctx, "exit");
  duk_push_int(ctx, exitCode);
  duk_int_t r = duk_pcall(ctx, 2);
  duk_pop_2(ctx);

but that doesn’t trigger the event and the return value is 1. What’s the correct way?

[svaarala]

Maybe it’d be helpful to have a wiki page with a table containing the Duktape API calls and the Ecmascript equivalents. Behavior of the “this” binding is not always well understood because you don’t deal with it as directly in Ecmascript code as you do in the C API.

[mike-lischke]

@svaarala That looks very concise and yet covers all relevant cases. That’s how it should be 😃 The only improvement I’d like to see is code formatting in the table. And maybe a word or 2 about duk_call_method vs. duk_call_prop.