(Java) Call a JavaScript Function Returning a Boolean

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Note: This example requires Chilkat v11.4.0 or greater.

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import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    boolean success = false;

    // This is the JavaScript function we'll call:

    // function isEven(number) {
    //     return number % 2 === 0;
    // }

    CkStringBuilder sbScript = new CkStringBuilder();
    sbScript.Append("function isEven(number) { return number % 2 === 0; }");

    CkJs js = new CkJs();

    CkJsonObject result = new CkJsonObject();
    result.put_EmitCompact(false);

    // Call Eval to add the function to the context's global object
    success = js.Eval(sbScript,result);
    if (success == false) {
        // Examine the result for an exception.
        System.out.println(result.emit());

        // Also examine the LastErrorText.
        System.out.println(js.lastErrorText());
        return;
        }

    // ------------------------------------------------------------------------------
    // Call the function isEven(8)

    CkJsonObject funcCall = new CkJsonObject();

    // Create JSON specifying the function name and arguments

    // {
    //   "name": "isEven",
    //   "args": [ 8 ]
    // }

    funcCall.UpdateString("name","isEven");
    funcCall.UpdateInt("args[0]",8);

    success = js.CallFunction(funcCall,result);
    if (success == false) {
        // Examine the result for an exception.
        System.out.println(result.emit());

        // Also examine the LastErrorText.
        System.out.println(js.lastErrorText());
        return;
        }

    System.out.println(result.emit());

    // Output:
    // {
    //   "type": "bool",
    //   "value": true
    // }

    boolean retval = result.BoolOf("value");
    System.out.println(retval);

    // Output:
    // true
  }
}