Java

Call a JavaScript Function Passing an Object Argument

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Demonstrates how to call a JavaScript function with an argument that is an object. Java

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 describeCar(car) {
    // 	console.log(`This is a ${car.year} ${car.make} ${car.model}.`);
    // }

    CkStringBuilder sbScript = new CkStringBuilder();
    sbScript.Append("function describeCar(car) { console.log(`This is a ${car.year} ${car.make} ${car.model}.`); }");

    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 describeCar(car)

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

    // Create JSON specifying the function name and arguments
    // In this case, there is only 1 argument, and it is an object.

    // {
    //   "name": "describeCar",
    //   "args": [
    //     {
    //       "make": "Toyota",
    //       "model": "Corolla",
    //       "year": 2022
    //     }
    //   ]
    // }

    funcCall.UpdateString("name","describeCar");

    // Create the JSON object that is the argument.
    CkJsonObject arg = new CkJsonObject();
    arg.UpdateString("make","Toyota");
    arg.UpdateString("model","Corolla");
    arg.UpdateInt("year",2022);

    // Create the arguments array.
    CkJsonArray argsArray = new CkJsonArray();
    argsArray.AddObjectCopyAt(0,arg);

    // Add the "args" array to the funcCall.
    funcCall.AppendArrayCopy("args",argsArray);

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

    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());

    // The describeCar JavaScript function returns nothing. 
    // Therefore, the result is "undefined".

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

    // However, the function emitted text to the console.

    CkStringBuilder sbOut = new CkStringBuilder();
    js.ConsoleOutputSb(sbOut);
    System.out.println(sbOut.getAsString());

    // Output:
    // This is a 2022 Toyota Corolla.

    // -----------------------------------------------------------
    // Note: If the object argument is simple, this is an alternative
    // and simpler way of creating the funcCall:

    funcCall.Clear();
    funcCall.UpdateString("name","describeCar");
    funcCall.UpdateString("args[0].make","Toyota");
    funcCall.UpdateString("args[0].model","Corolla");
    funcCall.UpdateInt("args[0].year",2022);
    System.out.println(funcCall.emit());
  }
}