Doubt about how to implement my code

[ccxvii]

Doubt about how to implement my code

[ccxvii]

A few misconceptions that need to be cleared up.

js_loadstring pushes an anonymous function that when run executes the code in the string. In your example, the function created by js_loadstring will define another function called myFunction when it is run.

The "this" value you need to push when calling a function is the value that 'this' will be bound to when executing the function. If you don't know or understand what this means, just use js_pushundefined.

js_newstate(NULL, NULL, JS_STRICT);
js_loadstring(J, "myfun", "function myFunction(p1, p2) { return p1+p2; }");
js_pushundefined(J); // we don't have a 'this' object
js_call(J, 0); // execute the script function that defines myFunction

Now we have run the code that defines myFunction. Now you can use it, like so:

js_getglobal(J, "myFunction"); // get the myFunction object
js_pushundefined(J;) // no this binding here either
js_pushnumber(J, 2); // argument 1
js_pushnumber(J, 3); // argument 2
js_call(J, 2); // call with 2 arguments
ret = js_tonumber(J, -1); // read return value
js_pop(J, 1); // pop return value to clean up stack

[avih]

js_loadfile gets a file name and compiles (parses) the file's content - it does not yet run it.

js_loadstring is the same, but you're providing the content of the file as the other argument. I.e. the vm thinks it loads a file with some name (for stack traces), but it never actually touches the disk, and takes your string as its content instead.

On both cases, after parsing, you need to also run it to actually apply the code (which in your case will end up with a global function myFunction).

So right after your js_loadstring, you need to "call" the parsed content to also run it, and you call it like you call anything else in mujs - push a this value, e.g. js_pushglobal(J); and js_call(J, 0); (no arguments).

The rest of your code should now work.

Alternatively, you can shorten this triplet (parse content, push this, call it to run it) to one command: js_dostring(J, <content-string>), which you can use instead of your js_loadstring, and it should work.

[AsierRF]

First of all, thanks for your help.

The code right now prints "Nan" as result.

I am afraid I did not understand how I can do this that you mention:

So right after your js_loadstring, you need to "call" the parsed content to also run it, and you call it like you call anything else in mujs

Based on the reference page, the function js_loadstring already pushes the function after compiling. And I can't find any function in the reference page that is used to call the functions. Could you please right the required functions structure?

An extra question related to js_dostring. Can I also set the input variables and get the return values if I use js_dostring?

[AsierRF]

Thanks a lot for your help.
The code works fine and now I understand the process.
I would suggest you add this or a similar example to the "Examples" page. I think it would help people understand it better.