Adds optional callback method (logger) for Observable.log/spy()

bacon-vs-kefir-api.md

@@ -60,7 +60,7 @@
 | Use `unsub` function, or `Bacon.noMore` | `obs.offError(fn)` |  |
 | Use `unsub` function, or `Bacon.noMore` | `obs.offEnd(fn)` |  |
 | Use `unsub` function, or `Bacon.noMore` | `obs.offAny(fn)` |  |
-| `obs.log([name])` | `obs.log([name])` | The log format is different. Kefir returns `this` unlike Bacon, that returns `unusb` function |
+| `obs.log([name])` | `obs.log([name, fn])` | The log format is different. Kefir returns `this` unlike Bacon, that returns `unusb` function |
 | Use `unsub` function | `obs.offLog([name])` |  |
 | `obs.name(newName)` | `obs.setName(newName)` |  |
 | `observable.withDescription(param...)` | No alt.  |  |

docs-src/descriptions/main-methods.pug

@@ -155,8 +155,8 @@ pre(title='console output')
 +descr-method('off-any', 'offAny', 'obs.offAny(callback)').
   Unsubscribes an #[b onAny] subscriber.
 
-+descr-method('log', 'log', 'obs.log([name])').
-  Turns on logging of any event to the browser console.
++descr-method('log', 'log', 'obs.log([name, fn])').
+  Turns on logging of any event to the browser console (default) or using specified callback function.
   Accepts an optional #[b name] argument that will be shown in the log if provided.
 
 pre.javascript(title='example')
@@ -174,8 +174,8 @@ pre(title='console output')
   Turns off logging. If #[b .log] was called with a #[b name] argument,
   #[b offLog] must be called with the same #[b name] argument.
 
-+descr-method('spy', 'spy', 'obs.spy([name])').
-  Turns on spying of any event to the browser console. Similar to
++descr-method('spy', 'spy', 'obs.spy([name, fn])').
+  Turns on spying of any event to the browser console (default) or using specified callback function. Similar to
   #[b .log], however #[b .spy] will not cause the stream to activate by itself.
   Accepts an optional #[b name] argument that will be shown in the log if provided.
 

src/observable.js

@@ -162,14 +162,14 @@ extend(Observable.prototype, {
     return this
   },
 
-  log(name = this.toString()) {
+  log(name = this.toString(), logger = console.log) {
     let isCurrent
     let handler = function(event) {
       let type = `<${event.type}${isCurrent ? ':current' : ''}>`
       if (event.type === END) {
-        console.log(name, type)
+        logger(name, type)
       } else {
-        console.log(name, type, event.value)
+        logger(name, type, event.value)
       }
     }
 
@@ -199,13 +199,13 @@ extend(Observable.prototype, {
     return this
   },
 
-  spy(name = this.toString()) {
+  spy(name = this.toString(), logger = console.log) {
     let handler = function(event) {
       let type = `<${event.type}>`
       if (event.type === END) {
-        console.log(name, type)
+        logger(name, type)
       } else {
-        console.log(name, type, event.value)
+        logger(name, type, event.value)
       }
     }
     if (this._alive) {

test/specs/log.js

@@ -30,7 +30,7 @@ describe('log', () => {
     })
   })
 
-  describe('console', () => {
+  describe('default logger', () => {
     let stub
     beforeEach(() => (stub = sinon.stub(console, 'log')))
 
@@ -68,4 +68,18 @@ describe('log', () => {
       })
     })
   })
+
+  describe('custom logger', () => {
+    it('should log using custom logger function', () => {
+      const a = stream()
+      const logger = sinon.fake()
+      a.log('logged', logger)
+      expect(a).to.emit([value(1), value(2), value(3)], () => {
+        send(a, [value(1), value(2), value(3)])
+        expect(logger).to.have.been.calledWith('logged', '<value>', 1)
+        expect(logger).to.have.been.calledWith('logged', '<value>', 2)
+        expect(logger).to.have.been.calledWith('logged', '<value>', 3)
+      })
+    })
+  })
 })

test/specs/spy.js

@@ -30,7 +30,7 @@ describe('spy', () => {
     })
   })
 
-  describe('console', () => {
+  describe('default logger', () => {
     let stub
     beforeEach(() => (stub = sinon.stub(console, 'log')))
 
@@ -68,4 +68,18 @@ describe('spy', () => {
       })
     })
   })
+
+  describe('custom logger', () => {
+    it('should log using custom logger function', () => {
+      const a = stream()
+      const logger = sinon.fake()
+      a.spy('spied', logger)
+      expect(a).to.emit([value(1), value(2), value(3)], () => {
+        send(a, [value(1), value(2), value(3)])
+        expect(logger).to.have.been.calledWith('spied', '<value>', 1)
+        expect(logger).to.have.been.calledWith('spied', '<value>', 2)
+        expect(logger).to.have.been.calledWith('spied', '<value>', 3)
+      })
+    })
+  })
 })