React Native Requires Chilkat v11.4.0+

Call a JavaScript Function Passing an Array Argument

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Demonstrates how to call a JavaScript function with an argument that is an array. React Native

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

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

  // function calculateTotal(numbers) {
  //   console.log(numbers);
  //   let total = 0;
  //   
  //   // Loop through every number in the array
  //   for (const num of numbers) {
  //     console.log(num);
  //     total += num;
  //   }
  //   
  //   return total;
  // }

  const sbScript = new StringBuilder();
  try {
    sbScript.loadFile('js_function_array_arg.js', 'utf-8');
  } catch {
    console.log(sbScript.lastErrorText);
    return;
  }

  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 calculateTotal(numbers)

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

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

  funcCall.updateString('name', 'calculateTotal');

  // Create the arguments array.
  const argsArray = new JsonArray();

  // The 1st argument in the arguments array is itself an array.
  // Passing -1 indicates to append to the array.
  const arg = new JsonArray();
  argsArray.addArrayAt2(-1, arg);

  // Fill in the values for the 1st argument.
  arg.addNumberAt(-1, '10.50');
  arg.addNumberAt(-1, '20.00');
  arg.addNumberAt(-1, '5.25');

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

  console.log(funcCall.emit());

  // The funcCall is as follows.  Notice that the 1st (and only) argument is an array.

  // {
  //   "name": "calculateTotal",
  //   "args": [
  //     [
  //       10.50,
  //       20.00,
  //       5.25
  //     ]
  //   ]
  // }

  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());

  // Result:
  // {
  //   "type": "double",
  //   "value": 35.75
  // }

  // The function also emitted text to the console.

  const sbOut = new StringBuilder();
  js.consoleOutputSb(sbOut);
  console.log(sbOut.getAsString());

  // Output:
  // 10.5,20,5.25
  // 10.5
  // 20
  // 5.25

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

  funcCall.clear();
  funcCall.updateString('name', 'calculateTotal');
  funcCall.updateNumber('args[0][0]', '10.50');
  funcCall.updateNumber('args[0][1]', '20.00');
  funcCall.updateNumber('args[0][2]', '5.25');
  console.log(funcCall.emit());
}

JavaScript

function calculateTotal(numbers) {
  console.log(numbers);
  let total = 0;
  
  // Loop through every number in the array
  for (const num of numbers) {
    console.log(num);
    total += num;
  }
  
  return total;
}