React Native Requires Chilkat v11.4.0+

Call a JavaScript Function Returning a String

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Demonstrates how to call a JavaScript function that returns a string. React Native

import { Js, JsonObject, StringBuilder } from '@chilkat/react-native'

async function chilkatExample() {
  // This is the JavaScript function we'll call:

  // function greet(name) {
  //     return "Hello, " + name + "!";
  // }

  const sbScript = new StringBuilder();
  sbScript.append('function greet(name) { return "Hello, " + name + "!"; }');

  const js = new Js();

  const result = new JsonObject();
  result.emitCompact = false;

  // Call Eval to add the function to the context's global object
  try {
    await js.evalAsync(sbScript, result);
  } catch {
    // Examine the result for an exception.
    console.log(result.emit());

    // Also examine the LastErrorText.
    console.log(js.lastErrorText);
    return;
  }

  // ------------------------------------------------------------------------------
  // Call the function greet("Michael")

  const funcCall = new JsonObject();

  // Create JSON specifying the function name and arguments

  // {
  //   "name": "greet",
  //   "args": [ "Michael" ]
  // }

  funcCall.updateString('name', 'greet');
  funcCall.updateString('args[0]', 'Michael');

  try {
    await js.callFunctionAsync(funcCall, result);
  } catch {
    // Examine the result for an exception.
    console.log(result.emit());

    // Also examine the LastErrorText.
    console.log(js.lastErrorText);
    return;
  }

  console.log(result.emit());

  // Output:
  // {
  //   "type": "string",
  //   "value": "Hello, Michael!"
  // }

  const retval = result.stringOf('value');
  console.log(retval);

  // Output:
  // Hello, Michael!
}