Ruby

Call a JavaScript Function Returning an Integer

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Demonstrates how to call a JavaScript function that returns an integer. Ruby

require 'chilkat'

success = false

#  ----------------------------------------------------------------------------------
#  The Javascript function called in this example is shown at the bottom of this page.
#  -----------------------------------------------------------------------------------

#  In this example, we'll load the Javascript function definition from a file.
#  It doesn't need to come from a file.  It could just as easily be loaded from a string.
sbScript = Chilkat::CkStringBuilder.new()
success = sbScript.LoadFile("js_call_function.js","utf-8")
if (success == false)
    print sbScript.lastErrorText() + "\n";
    exit
end

#  Note: Each instance of a Chilkat Js object automatically establishes
#  its own internal runtime and context.  Applications do not need to explicitly create
#  the JavaScript runtime or context.
js = Chilkat::CkJs.new()

result = Chilkat::CkJsonObject.new()
result.put_EmitCompact(false)

#  Call Eval to add the function (shown at the bottom of this page) to the context's global object
success = js.Eval(sbScript,result)
if (success == false)
    #  Examine the result for an exception.
    print result.emit() + "\n";

    #  Also examine the LastErrorText.
    print js.lastErrorText() + "\n";
    exit
end

print result.emit() + "\n";

#  The expected output is "undefined":

#  {
#    "type": "undefined",
#    "value": "undefined"
#  }

#     When Eval processes a script containing only a function declaration,
#     it successfully performs the action (the function becomes defined).
#     However, since the script consists of a statement that produces no value,
#     the script's overall completion value is empty. In JavaScript, the
#     absence of a value is represented by `undefined`.
#  
#     Therefore, the Eval call returns `undefined`.

#  ------------------------------------------------------------------------------
#  Call the function calculateScore("Player1", 10, 20)

funcCall = Chilkat::CkJsonObject.new()

#  Create JSON defining the function call:

#  {
#    "name": "calculateScore",
#    "args": [ "Player1", 10, 20 ]
#  }

funcCall.UpdateString("name","calculateScore")
funcCall.UpdateString("args[0]","Player1")
funcCall.UpdateInt("args[1]",10)
funcCall.UpdateInt("args[2]",20)

funcCall.put_EmitCompact(false)
print funcCall.emit() + "\n";

success = js.CallFunction(funcCall,result)
if (success == false)
    #  Examine the result for an exception.
    print result.emit() + "\n";

    #  Also examine the LastErrorText.
    print js.lastErrorText() + "\n";
    exit
end

print result.emit() + "\n";

#  Output:

#  {
#    "type": "int",
#    "value": 37
#  }

retval = result.IntOf("value")
print "retval = " + retval.to_s() + "\n";

JavaScript

function calculateScore(name, pointsA, pointsB) {
    // Return length of name + both scores
    return name.length + pointsA + pointsB;
    }