React Native Requires Chilkat v11.4.0+

Call a JavaScript Function Returning a Boolean

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

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

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

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

  const sbScript = new StringBuilder();
  sbScript.append('function isEven(number) { return number % 2 === 0; }');

  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 isEven(8)

  const funcCall = new JsonObject();

  // Create JSON specifying the function name and arguments

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

  funcCall.updateString('name', 'isEven');
  funcCall.updateInt('args[0]', 8);

  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": "bool",
  //   "value": true
  // }

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

  // Output:
  // true
}