fix(library): fixes an issue with optional callbacks being required

Only the `scan` and `getStatus` methods should be required. This fixes a bug which threw and error

when other methods were called without providing a callback.

#32

readme.md

@@ -144,7 +144,7 @@ Or alternatively, the library can be included in a page as-is, and the QRScanner
 On the browser platform, performance is improved by running the processing-intensive scanning operation in a [Web Worker](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API). For more information about the browser platform, see [Browser Platform Specific Details](#browser).
 
 ## API
-With the exception of `QRScanner.scan(callback)`, all callbacks are optional.
+With the exception of `QRScanner.scan(callback)` and `QRScanner.getStatus(callback)`, all callbacks are optional.
 
 ### Prepare
 

src/browser/src/library.js

@@ -19,16 +19,28 @@ function QRScanner() {
       destroy: internal.destroy
   };
 
+  // always returns an executable function for use by the internal component
+  // if a callback is provided, use it
+  function getFunc(callback){
+    if(typeof callback === "function"){
+      return callback;
+    }
+    return function(){
+      // callback is not needed
+      return;
+    };
+  }
+
   // shim cordova's functionality for library usage
   var shimCordova = {
     exec: function(successCallback, errorCallback, className, functionName, inputArray){
       if(className !== 'QRScanner' || !functionList[functionName]){
         return errorCallback(0);
       }
       if(inputArray){
-        functionList[functionName](successCallback, errorCallback, inputArray);
+        functionList[functionName](getFunc(successCallback), getFunc(errorCallback), inputArray);
       } else {
-        functionList[functionName](successCallback, errorCallback);
+        functionList[functionName](getFunc(successCallback), getFunc(errorCallback));
       }
     }
   };

src/common/src/createQRScannerAdapter.js

@@ -49,6 +49,9 @@ function clearBackground() {
 }
 
 function errorCallback(callback) {
+  if (!callback) {
+    return null;
+  }
   return function(error) {
     var errorCode = parseInt(error);
     var QRScannerError = {};