calling javascript function from Qt Console application

[SherifOmran]

I have a js function that i need to evaluate from qt console application, and i am trying to learnt the QScriptEngine

so far i could read my function

double a;
a=engine.evaluate("(myfunc(2,3))").toNumber();

in my simplejsfn.js i have

function myfunc(p1, p2) { return p1*p2; }

but i dont get the expected output

[JonB]

@SherifOmran

but i dont get the expected output

It always helps then if you say what you do get as the output!! (E.g. for all I know, you haven't included your simplejsfn.js, so the function isn't defined.)

Although I know nothing about this, why not start out from a simpler, non-function expression, e.g. as per the docs example myEngine.evaluate("1 + 2");. Does that work?

Then the docs go on to give a simple function example:

QScriptValue fun = myEngine.evaluate("(function(a, b) { return a + b; })");
QScriptValueList args;
args << 1 << 2;
QScriptValue threeAgain = fun.call(QScriptValue(), args);

Does that work?

That's how I'd approach it....

[SherifOmran]

@JonB said in calling javascript function from Qt Consolt application:

QScriptValue threeAgain = fun.call(QScriptValue(), args);

I read the js function from a js file

QScriptEngine engine;
      QString fileName(":/simplejsfn.js");
      QFile scriptFile(fileName);
      scriptFile.open(QIODevice::ReadOnly);
      QTextStream stream(&scriptFile);
      QString contents = stream.readAll();
      scriptFile.close();

      QScriptValue fun = engine.evaluate(contents);
      QScriptValueList args;
      args << 1 << 2;
      QScriptValue threeAgain = fun.call(QScriptValue(), args);

The js file has the following

function myfunc(p1, p2) { return p1*p2; }

while debugging i see the qstring in content with the following

"function myfunc(p1, p2) { return p1*p2; }\n"

The value of threeAgain is invalid ..

When i write the function as you do inside the evaluate it works, however when the function is inside a QString it does not work !

[jsulm]

@SherifOmran What if you do

QString contents = stream.readAll().trimmed();

?

[SherifOmran]

@jsulm same result except /n is removed

[jsulm]

@SherifOmran Did you try to call https://doc.qt.io/qt-5/qscriptengine.html#uncaughtException to see whether there is an exception and if so what it is?

[SherifOmran]

i did not try because this is a very simple example. I took another approach to create a browser and load the js file

[JonB]

@SherifOmran
Creating a browser, if you do not want it for other purposes, just to evaluate some JS is a very "heavyweight" solution. Just saying....

[jsulm]

@SherifOmran You're adding a browser because it is a "very simple example"?!
In my opinion it would be way faster and easier to check for exceptions instead (you should do this anyway)...

[SherifOmran]

yes that is true, and it will be heavy, but i intent to run very complicated js file and if i can not run a simple test function, how will it be with a complicated script !
If any body can provide me a working example, this would be great.

[JonB]

@SherifOmran

qDebug() << contents;
      QScriptValue fun = engine.evaluate(contents);
qDebug() << engine.hasUncaughtException();
      QScriptValueList args;
      args << 1 << 2;
      QScriptValue threeAgain = fun.call(QScriptValue(), args);
qDebug() << engine.hasUncaughtException();
qDebug() << threeAgain.isValid();

would be an improvement which would take you 10 seconds.

[SherifOmran]

@JonB said in calling javascript function from Qt Console application:

qDebug() << engine.hasUncaughtException();

Same result ! I am compiling under Mac high sierra 10.13.6

      QString contents = "function myfunc(p1, p2) { return p1*p2; }";
      QScriptValue fun = engine.evaluate(contents);
      qDebug() << engine.hasUncaughtException();
      QScriptValueList args;
      args << 1 << 2;
      QScriptValue threeAgain = fun.call(QScriptValue(), args);
      qWarning() << engine.hasUncaughtException();
      bool A= threeAgain.isValid();

[SherifOmran]

Please test it on your side and let me know, if this simple code works. May be this is a bug ? I am using clang under mac high sierra.