Added possibility to log on each error.

README.md

@@ -29,7 +29,7 @@ When you call ```polly().executeForPromise(<your function>)``` the code assumes
 When you call ```polly().executeForNode(<your function that accepts a callback>)``` the code assumes that your code failed and needs to be retried when your function calls the callback with a first non null parameter indicating an error.
 
 ## Deciding what to do on failure
-Whenever a failure is detected Polly-js will try attempt to retry your action. 
+Whenever a failure is detected Polly-js will attempt to retry your action. 
 
 You get to control how a failure is retried by calling either ```polly().retry()``` or ```polly().waitAndRetry()```. 
 Both will retry the failing action but the ```polly().waitAndRetry()``` option adds a small delay before retrying. 
@@ -41,7 +41,6 @@ With ```polly().waitAndRetry()``` it will double the time between each try. If y
 Using ```polly().handle(<function>)``` you can decide if you want to retry a specific failure. For example you might want to retry an AJAX request returning a 404 response code but not one resulting in a 500 response code.
 The callback function specified in ```polly().handle()``` is called with watever error was received so you can use any property from there and you return true if you want to retry the action or false to stop retrying. 
 
-
 ## Usage
 
 Try to load the Google home page and retry twice if it fails.
@@ -113,6 +112,24 @@ const loadData = url => {
 const movies = await loadData("http://localhost:3000/movies.json");
 ```
 
+## Logging errors
+You can set a logger function to be called every time an error is detected.
+```JavaScript
+polly()
+    .logger(function(err){
+        console.error(err); //will be hit 2 times
+    })
+    .retry(2)
+    .executeForPromise(function () {
+        return requestPromise('http://foo.bar.com');
+    })
+    .then(function(result) {
+        //do some important stuff here
+    }, function(err) {
+        console.error('Failed trying three times', err);//third error is passed back to the caller
+    });
+```
+
 ## Acknowledgements
 
 The library is based on the [Polly NuGet package](https://www.nuget.org/packages/Polly/) by Michael Wolfenden

d.ts/polly-js.d.ts

@@ -22,6 +22,7 @@ declare module 'polly-js' {
       }
 
       interface Polly {
+        logger (fn: (err: any) => void): Polly;
         handle (fn: (err: any) => boolean): Polly;
         retry (numRetries: number): Retryable;
         waitAndRetry (delays: number[]): AsyncRetryable;

src/polly.js

@@ -31,6 +31,7 @@
             }
             catch (ex) {
                 if (count < config.count && config.handleFn(ex)) {
+                    config.loggerFn(err);
                     count++;
                 } else {
                     throw ex;
@@ -50,6 +51,7 @@
                     resolve(e);
                 }, function (e) {
                     if (count < config.count && config.handleFn(e)) {
+                        config.loggerFn(err);
                         count++;
                         execute();
                     } else {
@@ -75,6 +77,7 @@
                     var delay = config.delays.shift();
 
                     if (delay && config.handleFn(e)) {
+                        config.loggerFn(err);
                         count++;
                         setTimeout(execute, delay);
                     } else {
@@ -93,11 +96,11 @@
 
         function internalCallback(err, data) {
             if (err && count < config.count && config.handleFn(err)) {
+                config.loggerFn(err);
                 count++;
                 fn(internalCallback, {count: count});
             } else {
                 callback(err, data);
-
             }
         }
 
@@ -110,6 +113,7 @@
         function internalCallback(err, data) {
             var delay = config.delays.shift();
             if (err && delay && config.handleFn(err)) {
+                config.loggerFn(err);
                 count++;
                 setTimeout(function () {
                     fn(internalCallback, {count: count});
@@ -139,10 +143,19 @@
             delays: [defaults.delay],
             handleFn: function () {
                 return true;
+            },
+            loggerFn: function(err) {
             }
         };
 
         return {
+            logger: function (loggerFn) {
+                if (typeof loggerFn === 'function') {
+                    config.loggerFn = loggerFn;
+                }
+
+                return this;
+            },
             handle: function (handleFn) {
                 if (typeof handleFn === 'function') {
                     config.handleFn = handleFn;