adds sample implementation for update ADD case for #48

Author: nelsonic

Diff for: examples/todo-list/todo-app.js

@@ -6,6 +6,7 @@ if (typeof require !== 'undefined' ) { // require elm(ish) creating local copy
     route, section, span, strong, text, ul } = require('./elmish.js');
 } // in the browser elm(ish) functions are automatically be available
 
+
 var initial_model = {
   todos: [],
   hash: "#/"
@@ -19,23 +20,15 @@ var initial_model = {
  * @return {Object} updated_model - the transformed model.
  */
 function update(action, model, data) {
-  // console.log('model:', model);
   var new_model = JSON.parse(JSON.stringify(model)) // "clone" the model
-  // console.log('new_model:', new_model);
   switch(action) {                   // and an action (String) runs a switch
-    // case 'ADD':
-    //   new_model.todos.push({
-    //     id: model.todos.length + 1,
-    //     title: data,
-    //     done: false
-    //   });
-    //   break;
-    // case Dec:
-    //   new_model.counters[index] = model.counters[index] - 1;
-    //   break;
-    // case Res: // use ES6 Array.fill to create a new array with values set to 0:
-    //   new_model.counters[index] = 0;
-    //   break;
+    case 'ADD':
+      new_model.todos.push({
+        id: model.todos.length + 1,
+        title: data,
+        done: false
+      });
+      break;
     default: // if action unrecognised or undefined,
       return model; // return model unmodified
   }   // see: https://softwareengineering.stackexchange.com/a/201786/211301

Diff for: todo-list.md

@@ -511,9 +511,39 @@ You should see the assertion _fail_:
 ![update-add-item-test-failing](https://user-images.githubusercontent.com/194400/43639131-206b632c-9713-11e8-83ee-d0ecab0ac4ef.png)
 
 
+#### `ADD` item _Implementation_
 
+With the above test as your "guide",
+write the _bare minimum_ code necessary to make all assertions pass.
 
-#### `ADD` item _Implementation_
+_Sample_ implementation:
+```js
+/**
+ * `update` transforms the `model` based on the `action`.
+ * @param {String} action - the desired action to perform on the model.
+ * @param {Object} model - the App's (current) model (or "state").
+ * @param {String} data - the data we want to "apply" to the item.
+ * @return {Object} updated_model - the transformed model.
+ */
+function update(action, model, data) {
+  var new_model = JSON.parse(JSON.stringify(model)) // "clone" the model
+  switch(action) {                   // and an action (String) runs a switch
+    case 'ADD':
+      new_model.todos.push({
+        id: model.todos.length + 1,
+        title: data,
+        done: false
+      });
+      break;
+    default: // if action unrecognised or undefined,
+      return model; // return model unmodified
+  }   // see: https://softwareengineering.stackexchange.com/a/201786/211301
+  return new_model;
+}
+```
+the `case 'ADD'` is the _relevant_ code. <br />
+
+> Was _your_ implementation _similar_...?