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.