javascript-todo-list-tutorial
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Learn how to build a Todo List in JavaScript following Test Driven Development TDD!
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# Todo List App JavaScript Tutorial
A **_step-by-step_ tutorial** showing you how to
build a **Todo List App _from scratch_** in **JavaScript**.
[](https://travis-ci.org/dwyl/javascript-todo-list-tutorial)
[](http://codecov.io/github/dwyl/javascript-todo-list-tutorial?branch=master)
[](https://david-dm.org/dwyl/javascript-todo-list-tutorial)
[](https://david-dm.org/dwyl/javascript-todo-list-tutorial?type=dev)
[](https://github.com/dwyl/javascript-todo-list-tutorial/issues)
[](http://hits.dwyl.io/dwyl/javascript-todo-list-tutorial)
<!-- uncomment when service is working ... [](http://inch-ci.org/github/dwyl/javascript-todo-list-tutorial) -->
<a href="https://todomvc-app.herokuapp.com"
alt="Try the Demo on Heroku!">
<img src="https://user-images.githubusercontent.com/194400/45237254-10d5e980-b2d6-11e8-8281-b95452bde519.gif"
alt="Step one: learn JavaScript!">
</a>
</div>
> Before you continue, try the demo: https://todomvc-app.herokuapp.com <br />
> Add a few items to the list. Double-click/tap the item to edit it.
Check-off your todos and navigate the footer to filter for Active/Completed.
Try and "break" it! Refresh the page and notice how your todo items
are "still there" (_they were saved to `localStorage`!_).
Once you have had a "play" with the demo, come back and _build_ it!!
<hr />
## Why?
The _purpose_ of this **Todo List _mini_ project**
is to _practice_ your "VanillaJS" skills and
_consolidate_ your understanding of The Elm Architecture (TEA)
by creating a "real world" _useable_ App following _strict_
Documentation and Test Driven Development.
This will _show_ you that it's not only _possible_
to write docs and tests _first_,
you will see _first hand_ that **`code`** is **more concise**,
**well-documented** and thus **_easier_ to maintain**
and you will get your "work" done ***much faster***.
These are _foundational_ skills that will
pay **_immediate_ returns** on the time invested,
and will **`continue`** to **`return`** "**interest**"
for as long as you write (_and people use your_) software!
> _It's **impossible** to "**over-state**" how **vital writing tests first**
is to both your **personal effectiveness** and **long-term sanity**.
Thankfully, by the end of this chapter, you will see how **easy** it is._
## What?
Build a fully functional "Todo List" Application! <br />
Along the way we will cover:
+ [x] Building an App using a pre-made CSS Styles/Framework!
+ [x] The Document Object Model (DOM) + JSDOM
+ [x] Browser Routing/Navigation
+ [x] Local Storage for Offline Support
+ [x] Keyboard event listeners for rapid todo list creation and editing!
We will be abstracting all "architecture" related ("generic") code
into a "mini frontend framework" called "***elmish***".
(_elmish is inspired by Elm but only meant for educational purposes!_)
The journey to creating **elmish** is captured in
[**`elmish.md`**](https://github.com/dwyl/javascript-todo-list-tutorial/blob/master/elmish.md)
and fully documented code is in **`elmish.js`**.
This means our Todo List App can be as concise
and "declarative" as possible.
### Todo List?
If you are _unfamiliar_ with Todo lists, simply put:
they are a way of keeping a list of the tasks that need to be done. <br />
see: https://en.wikipedia.org/wiki/Time_management#Setting_priorities_and_goals
Todo Lists or "Checklists" are the _best_ way of tracking tasks. <br />
Atul Gawande wrote a _superb_ book on this subject: <br />
https://www.amazon.com/Checklist-Manifesto-How-Things-Right/dp/0312430000 <br />
Or if you don't have time to read,
watch: https://www.youtube.com/results?search_query=checklist+manifesto
### TodoMVC?
If you have not come across TodoMVC before,
it's a website that showcases various "frontend" frameworks
using a common user interface (UI): a Todo List Application.
We _highly recommend_ checking out the following links:
+ Website: http://todomvc.com
+ GitHub project: https://github.com/tastejs/todomvc
For our purposes we will simply be re-using the **TodoMVC `CSS`**
to make our TEA Todo List _look_ good
(_not have to "worry" about styles so we can **focus on functionality**_).
All the JavaScript code will be written "_from scratch_"
to ensure that everything is clear.
## _Who?_
This tutorial is for anyone/everyone who wants
to develop their "core" JavaScript skills (_without using a framework/library_)
while building a "real world" (_fully functional_) Todo List Application.
> As always, if you get "stuck", _please_ open an issue:
https://github.com/dwyl/javascript-todo-list-tutorial/issues
by opening a question you help _everyone_ learn more effectively!
### Prerequisites
Most beginners with basic JavaScript and HTML knowledge
should be able to follow this example without any prior experience.
The code is commented and the most "complex" function is an event listener.
With that said, if you feel "stuck" at any point,
please consult the recommend reading (_and Google_)
and if you cannot find an answer,
please open an issue!
### Recommended reading:
+ Test Driven Developement: https://github.com/dwyl/learn-tdd
+ Tape-specific syntax: https://github.com/dwyl/learn-tape
+ Elm Architecture: https://github.com/dwyl/learn-elm-architecture-in-javascript
## _How?_
Start by cloning this repository to your `localhost`
so that you can follow the example/tutorial offline:
```sh
git clone https://github.com/dwyl/javascript-todo-list-tutorial.git
```
Install the `devDependencies` so you can run the tests:
```sh
cd javascript-todo-list-tutorial && npm install
```
Now you have _everything_ you need to build a Todo List from scratch!
### `Elm`(_ish_) ?
In order to _simplify_ the code for our Todo List App,
we _abstracted_ much of the "_generic_" code
into a "front-end micro framework" called `Elm`(_ish_).
The functions & functionality of `Elm`(_ish_) should be _familiar_ to you
so you _should_ be able to build the Todo List using the `Elm`(_ish_)
helper functions e.g: `mount`, `div`, `input` and `route`.
You can _opt_ to _either_: <br />
**a)** read the `Elm`(_ish_) docs/tutorial
[`elmish.md`](https://github.com/dwyl/learn-elm-architecture-in-javascript/blob/master/elmish.md)
***`before`*** building the Todo List App -
this will give you both TDD practice
and a deeper understanding of building a micro framework.
i.e. "**_prospective_ learning**"<br />
**b)** refer the `Elm`(_ish_) docs/tutorial
[`elmish.md`](https://github.com/dwyl/learn-elm-architecture-in-javascript/blob/master/elmish.md)
***`while`*** building the Todo List App when you "**_need_ to know**"
how one of the helper functions works. i.e. "**_contextual_ learning**" <br />
**c)** **only _consult_** the `Elm`(_ish_) docs/tutorial
[`elmish.md`](https://github.com/dwyl/learn-elm-architecture-in-javascript/blob/master/elmish.md)
***`if`*** you are "stuck" ***`while`*** building the Todo List App.
i.e. "**_debug_ learning**" <br />
The choice is yours; there is no "_right_" way to learn.
### Testing & Documentation?
_Before_ diving into _building_ the Todo List App,
we need to consider how we are going to _test_ it.
By ensuring that we follow **TDD** from the _start_ of an App,
we will have ["***no surprises***"](https://youtu.be/u5CVsCnxyXg)
and _avoid_ having to "correct" any
["***bad habits***"](https://www.youtube.com/results?search_query=Destiny%27s+Child+Bad+Habit).
We will be using **Tape** and **JSDOM** for testing
both our functions and the final application.
If you are `new` to either of these tools,
please see:
[github.com/dwyl/**learn-tape**](https://github.com/dwyl/learn-tape)
and
[**front-end**-with-tape.md](https://github.com/dwyl/learn-tape/blob/master/front-end-with-tape.md)
We will be using **JSDOC** for documentation.
Please see [our tutorial](https://github.com/dwyl/learn-jsdoc) if this is new to you.
#### Create Files
In your editor/terminal create the following files:
+ `test/todo-app.test.js`
+ `lib/todo-app.js`
+ `index.html`
These file names should be self-explanatory, but if unclear,
`todo-app.test.js` is where we will write the tests for our
Todo List App.
`todo-app.js` is where all the JSDOCs and functions
for our Todo List App will be written.
#### Test Setup
In order to run our test(s), we need some "setup" code
that "requires" the libraries/files so we can _execute_ the functions.
In the `test/todo-app.test.js` file, type the following code:
```js
const test = require('tape'); // https://github.com/dwyl/learn-tape
const fs = require('fs'); // to read html files (see below)
const path = require('path'); // so we can open files cross-platform
const html = fs.readFileSync(path.resolve(__dirname, '../index.html'));
require('jsdom-global')(html); // https://github.com/rstacruz/jsdom-global
const app = require('../lib/todo-app.js'); // functions to test
const id = 'test-app'; // all tests use 'test-app' as root element
```
> Most of this code should be _familiar_ to you
if you have followed previous tutorials.
> If anything is _unclear_ please revisit
[https://github.com/dwyl/**learn-tape**](https://github.com/dwyl/learn-tape)
and
[**front-end**-with-tape.md](https://github.com/dwyl/javascript-todo-list-tutorial/blob/master/front-end-with-tape.md)
If you attempt to run the test file: `node test/todo-app.test.js`
you should see no output. <br />
(_this is expected as we haven't written any tests yet!_)
### `model`
The `model` for our Todo List App is **_boringly_ simple**.
All we need is an `Object` with a
`todos` key which has an Array of Objects as it's value:
```js
{
todos: [
{ id: 1, title: "Learn Elm Architecture", done: true },
{ id: 2, title: "Build Todo List App", done: false },
{ id: 3, title: "Win the Internet!", done: false }
]
}
```
`todos` is an `Array` of `Objects` and each Todo (Array) item
has 3 keys:
+ `id`: the index in the list.
+ `title`: the title/description of the todo item.
+ `done`: a `boolean` indicating if the item is complete or still "todo".
#### What about the `count` of items ?
> The TodoMVC Specification requires us to display a **`counter`**
of the items in the Todo list:
https://github.com/tastejs/todomvc/blob/master/app-spec.md#counter
In order to display the `count` of items in the Todo list,
we _could_ store 3 values in the model:
+ `total_items` - the total number of items, in this case 3.
+ `completed_items` - the number of completed items. in this case 1.
+ `incomplete_items` - the number of items still to be done; 2.
Each time a `new item` is added to the list
we would need to update
both the `total_items`
and the `incomplete_items`
values in the `model`.
And each time an `item` gets checked off as "done",
we would need to update _both_ the `incomplete_items`
and the `completed_items`.
This is _unnecessary_ effort we can avoid.
We can simply _compute_ these values based on the data in the `todos` Array
and display them for the user without storing any additional data.
Instead of _storing_ any additional data for a `counter` in the model
(_the count of active and completed Todo items_),
we will _compute_ the count and display the count at "runtime".
We don't _need_ to store any additional data in the `model`.
This may use a few CPU cycles computing the `count`
each time the view is rendered but that's "OK"!
Even on an _ancient_ Android device
this will only take a millisecond to compute and
won't "slow down" the app or affect UX.
See below for how the three counts are computed.
e.g: in the model above there are 3 todo items in the `todos` Array;
2 items which are "active" (`done=false`)
and 1 which is "done" (`done=true`).
#### `model` _Test_
Given that the `model` is "just data"
(
_it has **no** "**methods**" because `Elm`(ish) is_
["***Functional***"](https://en.wikipedia.org/wiki/Functional_programming)
_**not**_
["***Object Oriented***"](https://en.wikipedia.org/wiki/Object-oriented_programming)
),
there is no _functionality_ to test.
We are merely going to test for the "shape" of the data.
In the `test/todo-app.test.js` file, append following test code:
```js
test('todo `model` (Object) has desired keys', function (t) {
const keys = Object.keys(app.model);
t.deepEqual(keys, ['todos', 'hash'], "`todos` and `hash` keys are present.");
t.true(Array.isArray(app.model.todos), "model.todos is an Array")
t.end();
});
```
If you _run_ this test in your terminal:
```sh
node test/todo-app.test.js
```
You should see _both_ assertions _fail_:
#### `model` _Implementation_
Write the _minimum_ code required to _pass_ this test in `todo-app.js`.
e.g:
```js
/**
* initial_model is a simple JavaScript Object with two keys and no methods.
* it is used both as the "initial" model when mounting the Todo List App
* and as the "reset" state when all todos are deleted at once.
*/
var initial_model = {
todos: [], // empty array which we will fill shortly
hash: "#/" // the hash in the url (for routing)
}
/* module.exports is needed to run the functions using Node.js for testing! */
/* istanbul ignore next */
if (typeof module !== 'undefined' && module.exports) {
module.exports = {
model: initial_model
}
}
```
Once you save the `todo-app.js` file and re-run the tests.
```sh
node test/todo-app.test.js
```
You _should_ expect to see both assertions _passing_:
We're off to a _great_ start! Let's tackle some actual _functionality_ next!
<br />
### `update`
The `update` function is the
["brain"](https://www.youtube.com/results?search_query=Pinky+and+The+Brain)
of the App.
#### `update` JSDOC
The **`JSDOC`** for our `update` function is:
```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 data ("state").
* @return {Object} new_model - the transformed model.
*/
```
#### `update` Test > `default case`
As with the `update` in our `counter` example
the function body is a `switch` statement
that "decides" how to handle a request based on the `action`
(_also known as the "message"_).
Given that we _know_ that our `update` function "skeleton"
will be a `switch` statement
(_because that is the "TEA" pattern_)
a good test to _start_ with is the `default case`.
Append the following test code in `test/todo-app.test.js`:
```js
test('todo `update` default case should return model unmodified', function (t) {
const model = JSON.parse(JSON.stringify(app.model));
const unmodified_model = app.update('UNKNOWN_ACTION', model);
t.deepEqual(model, unmodified_model, "model returned unmodified");
t.end();
});
```
If you _run_ this test in your terminal:
```sh
node test/todo-app.test.js
```
You should see the assertion _fail_:
#### `update` Function Implementation > `default case`
Write the _minimum_ code necessary to pass the test.
> Yes, we could just write:
```js
function update (action, model) { return model; }
```
And that _would_ make the test _pass_. <br />
But, in light of the fact that we **know** the `update`
function body will contain a `switch` statement,
make the test pass by returning the `model` _unmodified_ in the `default` case.
e.g:
```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").
* @return {Object} new_model - the transformed model.
*/
function update(action, model) {
switch (action) { // action (String) determines which case
default: // if action unrecognised or undefined,
return model; // return model unmodified
} // default? https://softwareengineering.stackexchange.com/a/201786/211301
}
```
When you re-run the test(s) in your terminal:
```sh
node test/todo-app.test.js
```
You should see this assertion pass:
Now that we have a _passing_ test
for the `default case` in our `update` function,
we can move on to
thinking about the first (_and most fundamental_) piece
of _functionality_ in the Todo List App: Adding an item to the list.
### `ADD` an `item` to the Todo List
This is both the _first_ "feature" a "user" will encounter and
_by_ far the most _used_ feature of a Todo List. <br />
(_by **definition** people add more items to their list than they finish,
to finish everything we would have to_
[***live forever***!](https://youtu.be/TDe1DqxwJoc))
#### `ADD` item _Acceptance Criteria_
Adding a new todo item's text should
append the todo item `Object` to the `model.todos` Array. <br />
Such that the `model` is transformed (_data is added_) in the following way:
_BEFORE_:
```js
{
todos: [],
hash: "#/"
}
```
_AFTER_:
```js
{
todos: [
{id: 1, "Add Todo List Item", done: false }
],
hash: "#/"
}
```
#### Hold On, That Doesn't Seem "_Right_" How Does Todo Item _Text_ Get Added?
While considering the "Acceptance Criteria"
for adding an item to the Todo List,
we _notice_ that our `update` **`JSDOC`**
and corresponding function "signature" (_defined above_) as:
```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").
* @return {Object} updated_model - the transformed model.
*/
function update(action, model) {
switch (action) { // action (String) determines which case
default: // if action unrecognised or undefined,
return model; // return model unmodified
} // default? https://softwareengineering.stackexchange.com/a/201786/211301
}
```
does not have a **parameter** for passing in the Todo List item Text (`title`),
i.e. how do we add "data" to the `model`...?
That's "_Oh kay_"! (_don't panic_!) <br />
If we **`try`** to think about implementation up-front,
we would _invariably_ be "over-thinking" things
and get "stuck" in the
["analysis paralysis"](https://en.wikipedia.org/wiki/Analysis_paralysis)
of
["***waterfall***"](https://en.wikipedia.org/wiki/Waterfall_model)
As you are _about_ to see, we can _easily_ change the function signature,
in the _next_ test _without affecting_ our exiting (_passing_) test!
As you _practice_ "DDD" & "TDD" you will begin to _appreciate_
and even _embrace_ the _mental agility_ that comes from
_not_ "over-thinking" things.
Whenever you encounter a "New Requirement"
(_or realise that you didn't **fully consider** the **original requirements**_),
you know that your _suite_ of tests has
"
[got your](https://www.urbandictionary.com/define.php?term=Got%20your%20back)
[back](https://youtu.be/gk2yOxTuLck)
". <br />
You can "_refactor_" a function's _implementation_ to your heart's content,
safe in the knowledge that all your _existing_ tests still pass.
i.e. the _rest_ of the app "**still works**" **_exactly_ as expected**.
We don't want to "mess with" either of the other two (_existing_) parameters,
both `action` and `model` have clearly defined purposes,
but we _need_ a way to pass "data" into the `update` function!
With that in mind, let's _amend_ the `update` **`JSDOC`** comment
and function signature to:
```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 - data we want to "apply" to the item. e.g: item Title.
* @return {Object} updated_model - the transformed model.
*/
function update(action, model, data) {
switch (action) { // action (String) determines which case
default: // if action unrecognised or undefined,
return model; // return model unmodified
} // default? https://softwareengineering.stackexchange.com/a/201786/211301
}
```
Without making _any_ other changes, re-run the tests:
```sh
node test/todo-app.test.js
```
_Everything_ should still pass:
Congratulations! You just _extended_ a function (_signature_)
without affecting any _existing_ tests.
#### `ADD` item _Test_
Append the following test code to your `test/todo-app.test.js` file:
```js
test('`ADD` a new todo item to model.todos Array via `update`', function (t) {
const model = JSON.parse(JSON.stringify(app.model)); // initial state
t.equal(model.todos.length, 0, "initial model.todos.length is 0");
const updated_model = app.update('ADD', model, "Add Todo List Item");
const expected = { id: 1, title: "Add Todo List Item", done: false };
t.equal(updated_model.todos.length, 1, "updated_model.todos.length is 1");
t.deepEqual(updated_model.todos[0], expected, "Todo list item added.");
t.end();
});
```
If you _run_ this test in your terminal:
```sh
node test/todo-app.test.js
```
You should see the assertion _fail_:
#### `ADD` item _Implementation_
With the above test as your "guide",
write the _bare minimum_ code necessary to make all assertions pass.
_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_...? <br />
> If you were able to make it _simpler_,
[please share!](https://github.com/dwyl/learn-elm-architecture-in-javascript/issues/48)
Once you have the test(s) _passing_ e.g:
Let's move on to the _next_ functionality!
<br />
### `TOGGLE` a Todo `item` to `done=true`
Checking off a todo item involves changing the value of the `done` property
from `false` to `true`. e.g:
_FROM_:
```js
{
todos: [
{id: 1, "Toggle a todo list item", done: false }
]
}
```
_TO_:
```js
{
todos: [
{id: 1, "Toggle a todo list item", done: true }
]
}
```
Given that we have already defined our `update` function above,
we can dive straight into writing a _test_:
#### `TOGGLE` item _Test_
Append the following test code to your `test/todo-app.test.js` file:
```js
test('`TOGGLE` a todo item from done=false to done=true', function (t) {
const model = JSON.parse(JSON.stringify(app.model)); // initial state
const model_with_todo = app.update('ADD', model, "Toggle a todo list item");
const item = model_with_todo.todos[0];
const model_todo_done = app.update('TOGGLE', model_with_todo, item.id);
const expected = { id: 1, title: "Toggle a todo list item", done: true };
t.deepEqual(model_todo_done.todos[0], expected, "Todo list item Toggled.");
t.end();
});
```
_execute_ the test:
```sh
node test/todo-app.test.js
```
You should see something _similar_ to the following:
#### `TOGGLE` item _Implementation_
With the above test as your "guide",
write the _minimum_ code necessary to make the test pass.
(_ensure that you continue to make a "copy" of the `model`
rather than "mutate" it_)
Once you make it _pass_ you should see:
> Try to make the test pass alone (or with your pairing partner).
If you get "stuck" see: [**`todo-app.js`**](https://github.com/dwyl/learn-elm-architecture-in-javascript/pull/45/commits/5d4ebc546101efe05644a05833d73caec77c32ae)
#### Hold On, Does This Work _Both_ Ways?
_Yes_, you _guessed_ it!
Choosing to name the `action` as "`TOGGLE`"
is _precisely_ because we don't _need_
to have a _**separate**_ function
to "undo" an item if it has been "checked off".
Append the following test code to your `test/todo-app.test.js` file:
```js
test('`TOGGLE` (undo) a todo item from done=true to done=false', function (t) {
const model = JSON.parse(JSON.stringify(app.model)); // initial state
const model_with_todo = app.update('ADD', model, "Toggle a todo list item");
const item = model_with_todo.todos[0];
const model_todo_done = app.update('TOGGLE', model_with_todo, item.id);
const expected = { id: 1, title: "Toggle a todo list item", done: true };
t.deepEqual(model_todo_done.todos[0], expected, "Toggled done=false >> true");
// add another item before "undoing" the original one:
const model_second_item = app.update('ADD', model_todo_done, "Another todo");
t.equal(model_second_item.todos.length, 2, "there are TWO todo items");
// Toggle the original item such that: done=true >> done=false
const model_todo_undone = app.update('TOGGLE', model_second_item, item.id);
const undone = { id: 1, title: "Toggle a todo list item", done: false };
t.deepEqual(model_todo_undone.todos[0],undone, "Todo item Toggled > undone!");
t.end();
});
```
You should not _need_ to modify any of the code in the `update` function.
The above test should just _pass_ based on the code you wrote above.
If it does _not_, then _revise_ your implementation
of the `TOGGLE case` in `update` until _all_ tests pass:
### `view` Function
It won't have "_escaped_" you that _so far_ we have not written _any_ code
that a _user_ can actually _interact_ with.
_So far_ we have _successfully_ added two `case` blocks in the `switch` statement
of our `update` function. We now have the two _basic_ functions required
to both `ADD` a new todo list item to the `model.todos` Array
_and_ check-off a todo list item as "done" using the `TOGGLE action`.
This is "_enough_" functionality to start _using_ the todo list (_ourselves_)
and **UX-testing** it with _prospective_ "***users***".
If you followed through the "Elm(ish)" tutorial
[`elmish.md`](https://github.com/dwyl/learn-elm-architecture-in-javascript/blob/master/elmish.md)
you will have seen that we created a _sample_ `view` in the last few _tests_
to "_exercise_" the DOM element creation functions.
This means that we _already know_ how to build a `view` for our Todo List App!
We "_just_" need to _adapt_ the `view` we made in `Elm`(_ish_) to display
the data in our `model`.
#### Sample `model` to Render in Our `view`
Let's return to the sample `model` from above:
```js
{
todos: [
{ id: 1, title: "Learn Elm Architecture", done: true },
{ id: 2, title: "Build Todo List App", done: false },
{ id: 3, title: "Win the Internet!", done: false }
],
hash: '#/' // the "route" to display
}
```
The model contains _three_ items in the `todos` Array. <br />
The first is complete (`done=true`)
whereas the second and third items are still "todo" (`done=false`).
This is what this `model` looks like in the "VanillaJS"
TodoMVC:
Our _quest_ in the next "pomodoro" is to re-create this
using the DOM functions we created in `Elm`(_ish_)!
#### Focus on Rendering The _List_ First
For now, _ignore_ the `<footer>` (_below the Todo List_)
and _just_ focus on rendering the _list_ itself.
In your web browser, open **Dev**eloper **Tools**
and _inspect_ the HTML for the Todo list:
http://todomvc.com/examples/vanillajs/
This is the HTML copied directly from the browser:
```html
<section class="main" style="display: block;">
<input class="toggle-all" type="checkbox">
<label for="toggle-all">Mark all as complete</label>
<ul class="todo-list">
<li data-id="1533501855500" class="completed">
<div class="view">
<input class="toggle" type="checkbox">
<label>Learn Elm Architecture</label>
<button class="destroy"></button>
</div>
</li>
<li data-id="1533501861171" class="">
<div class="view">
<input class="toggle" type="checkbox">
<label>Build Todo List App</label>
<button class="destroy"></button>
</div>
</li>
<li data-id="1533501867123" class="">
<div class="view"><input class="toggle" type="checkbox">
<label>Win the Internet!</label>
<button class="destroy"></button>
</div>
</li>
</ul>
</section>
```
> _**Note**: there is "redundant" markup in this HTML in the form of a `<div>`
inside the `<li>`, for now we are just replicating the HTML "faithfully",
we can "prune" it later._
From this HTMl we can write our
["**_Technical_ Acceptance Criteria**"](https://github.com/dwyl/learn-elm-architecture-in-javascript/issues/51):
+ [ ] Todo List items should be displayed as list items **`<li>`**
in an _unordered list_ **`<ul>`**.
+ [ ] Each Todo List item **`<li>`** should contain a **`<div>`**
with a **`class="view"`** which "wraps":
+ [ ] **`<input class="toggle" type="checkbox">`** - the "checkbox"
that people can "Toggle" to change the "state"
of the Todo item from "active" to "done"
(_which updates the model
From: `model.todos[id].done=false`
To: `model.todos[id].done=true`_)
+ [ ] **`<label>`** - the text content ("title") of the todo list item
+ [ ] **`<button class="destroy">`** - the button the person
can click/tap to **`delete`** a Todo item.
### Todo List `view` Test Assertions
Given the `model` (_above_),
+ [ ] There is a `<ul class="todo-list">` with 3 **`<li>`** (_list items_)
rendered in the `view`.
+ [ ] The ***first*** **`<li>`** has an **`<input type="checkbox">`**
which is _checked_ (`done=true`)
+ [ ] The ***remaining*** **`<li>'s`** have **`<input type="checkbox">`**
that are _unchecked_ (`done=false`)
Let's "tackle" the _first_ assertion _first_:
#### Render a _Single_ Todo List Item Using `render_list` Test
It's _always_ a good idea to "break apart" a test into smaller tests
because it means we will write smaller
(_and thus **more maintainable**_) "_composable_" functions.
With that in mind, let's add the following _test_ to `test/todo-app.test.js`:
```js
test.only('render_item HTML for a single Todo Item', function (t) {
const model = {
todos: [
{ id: 1, title: "Learn Elm Architecture", done: true },
],
hash: '#/' // the "route" to display
};
// render the ONE todo list item:
document.getElementById(id).appendChild(app.render_item(model.todos[0]))
const done = document.querySelectorAll('.completed')[0].textContent;
t.equal(done, 'Learn Elm Architecture', 'Done: Learn "TEA"');
const checked = document.querySelectorAll('input')[0].checked;
t.equal(checked, true, 'Done: ' + model.todos[0].title + " is done=true");
elmish.empty(document.getElementById(id)); // clear DOM ready for next test
t.end();
});
```
After saving the `test/todo-app.test.js` file, if you attempt to run it:
```sh
node test/todo-app.test.js
```
you will see something like this:
#### `render_list` Implementation
Given the test above, I added the following code to my `todo-app.js` file:
```js
/* if require is available, it means we are in Node.js Land i.e. testing! */
/* istanbul ignore next */
if (typeof require !== 'undefined' && this.window !== this) {
var { a, button, div, empty, footer, input, h1, header, label, li, mount,
route, section, span, strong, text, ul } = require('./elmish.js');
}
/**
* `render_item` creates an DOM "tree" with a single Todo List Item
* using the "elmish" DOM functions (`li`, `div`, `input`, `label` and `button`)
* returns an `<li>` HTML element with a nested `<div>` which in turn has the:
* `<input type=checkbox>` which lets users to "Toggle" the status of the item
* `<label>` which displays the Todo item text (`title`) in a `<text>` node
* `<button class="destroy">` lets people "delete" a todo item.
* see: https://github.com/dwyl/learn-elm-architecture-in-javascript/issues/52
* @param {Object} item the todo item object
* @return {Object} <li> DOM Tree which is nested in the <ul>.
* @example
* // returns <li> DOM element with <div>, <input>. <label> & <button> nested
* var DOM = render_item({id: 1, title: "Build Todo List App", done: false});
*/
function render_item(item) {
return (
li([
"data-id=" + item.id,
"id=" + item.id,
item.done ? "class=completed" : ""
], [
div(["class=view"], [
input(["class=toggle", "type=checkbox",
(item.done ? "checked=true" : "")], []),
label([], [text(item.title)]),
button(["class=destroy"])
]) // </div>
]) // </li>
)
}
```
Add the `render_item` to the `module.exports` at the end of the file:
```js
if (typeof module !== 'undefined' && module.exports) {
module.exports = {
model: initial_model,
update: update,
render_item: render_item, // export so that we can unit test
}
}
```
This will make the test pass:
Now that we have a `render_item` function
that renders a _single_ `<li>` (_todo list item_),
we can create another function which _uses_ the `render_item` in a "loop",
to create _several_ `<li>` nested in a `<ul>`.
#### `render_main` Test
Append the following test code to your `test/todo-app.test.js` file:
```js
test('render "main" view using (elmish) HTML DOM functions', function (t) {
const model = {
todos: [
{ id: 1, title: "Learn Elm Architecture", done: true },
{ id: 2, title: "Build Todo List App", done: false },
{ id: 3, title: "Win the Internet!", done: false }
],
hash: '#/' // the "route" to display
};
// render the "main" view and append it to the DOM inside the `test-app` node:
document.getElementById(id).appendChild(app.render_main(model));
// test that the title text in the model.todos was rendered to <label> nodes:
document.querySelectorAll('.view').forEach(function (item, index) {
t.equal(item.textContent, model.todos[index].title,
"index #" + index + " <label> text: " + item.textContent)
})
const inputs = document.querySelectorAll('input'); // todo items are 1,2,3
[true, false, false].forEach(function(state, index){
t.equal(inputs[index + 1].checked, state,
"Todo #" + index + " is done=" + state)
})
elmish.empty(document.getElementById(id)); // clear DOM ready for next test
t.end();
});
```
If you attempt to run this test:
```sh
node test/todo-app.test.js
```
you will see something like this:
Given your knowledge of implementing the `render_item` function above,
and your skills with JavaScript loops, create your `render_main` function,
to make the tests pass.
> If you get "stuck" there is a _reference_ implementation in:
[**`todo-app.js`**](https://github.com/dwyl/learn-elm-architecture-in-javascript/pull/45/commits/b6607478c3dbed048781932261af2981f4c6c405#diff-6be3e16fe7cfb4c00788d4d587374afdR76)
All our tests pass _and_ we have **100% test coverage**:
This means we are writing the "_bare minimum_" code necessary
to meet all acceptance criteria (_requirements_),
which is _both **faster** and **more maintainable**_! <br />
Onwards!
<br />
### `<footer>` Element [issues/53](https://github.com/dwyl/learn-elm-architecture-in-javascript/issues/53)
Referring again to the _rendered_ HTML
on http://todomvc.com/examples/vanillajs as our "guide":
#### Dev Tools > Elements (inspector)
#### Copy-paste the _rendered_ HTML
"_copy-pasted_" of the _rendered_ HTML from the Dev Tools:
```html
<footer class="footer" style="display: block;">
<span class="todo-count">
<strong>2</strong> items left
</span>
<ul class="filters">
<li>
<a href="#/" class="selected">All</a>
</li>
<li>
<a href="#/active">Active</a>
</li>
<li>
<a href="#/completed">Completed</a>
</li>
</ul>
<button class="clear-completed" style="display: block;">
Clear completed
</button>
</footer>
```
#### Technical Acceptance Criteria
These are the criteria (_checklist_) as described in [issues/53](https://github.com/dwyl/learn-elm-architecture-in-javascript/issues/53):
+ [ ] **`render_footer`** returns a **`<footer>`** DOM element which can be rendered directly to the `document` or _nested_ in another DOM element.
+ [ ] **`<footer>`** contains:
+ [ ] **`<span class="todo-count">`** which contains
+ [ ] a **`text`** node with: **"`{count}` item(s) left"**.
_pseudocode_:
`{model.todos.filter( (i) => { i.done==false })}`
item`{model.todos.length > 1 ? 's' : '' }` left
+ [ ] **`<ul>`** containing 3 **`<li>`** with the following links (**`<a>`**):
+ [ ] Show **`All`**: **`<a href="#/" class="selected">All</a>`**
+ [ ] **`class="selected"`** should only appear on the selected menu/navigation item.
this should be "driven" by the `model.hash` property.
+ [ ] Show **`Active`**: **` <a href="#/active">Active</a>`**
+ [ ] Show **`Completed`**: **`<a href="#/completed">Completed</a>`**
+ [ ] **`<button class="clear-completed" style="display: block;">`**
will **_Clear_ all `Completed`** items.
_sample code_: <br />
`new_model.todos = model.todos.filter(function(item) { return item.done === false })`
#### _Estimate_ Time Required to Write `render_footer` Function
"_armed_" with the acceptance criteria _checklist_
and the
["***informative prior***"](https://en.wikipedia.org/wiki/Prior_probability#Informative_priors)
(_the **experience** we have **already** gained_)
from building the previous view functions
**`render_item`** and **`render_main`**
we ***estimate*** with _reasonable confidence_
that it will take us
**25 minutes** (_**one** "**pomodoro**_)
to:
+ [ ] Craft the **`JSDOC`** comment _documenting_ the `render_footer` function
so that all future developers will _easily_ understand what the function does.
+ [ ] Write a (unit) **test** covering the acceptance criteria (_test first!_)
+ [ ] Write the (_bare minimum_) code to ***pass*** the test assertions.
> _**Note On Time Estimates**: if it takes **longer** than **25 mins** "budget",
**don't panic** or feel like you have "failed",
it's not a "problem" ...
it's just "**more data**" (knowledge/experience)
that you can incorporate into improving **future estimates**!
over time you will get **really good** at estimating,
this is just a **starting point**_
#### `render_footer` `JSDOC` Comment Documentation
Here is a sample comment which documents the **`render_footer`** function:
```js
/**
* `render_footer` renders the `<footer class="footer">` of the Todo List App
* which contains count of items to (still) to be done and a `<ul>` "menu"
* with links to filter which todo items appear in the list view.
* @param {Object} model - the App's (current) model (or "state").
* @return {Object} <section> DOM Tree which containing the <footer> element.
* @example
* // returns <footer> DOM element with other DOM elements nested:
* var DOM = render_footer(model);
*/
```
Write your _own_ JSDOC or add these lines to your **`todo-app.js`** file.
#### `render_footer` Test
Here is a sample test you can add to your `test/todo-app.test.js` file:
(_if you feel confident in your TDD skills,
you could **`try`** to write your own test/assertions..._)
```js
test.only('render_footer view using (elmish) HTML DOM functions', function (t) {
const model = {
todos: [
{ id: 1, title: "Learn Elm Architecture", done: true },
{ id: 2, title: "Build Todo List App", done: false },
{ id: 3, title: "Win the Internet!", done: false }
],
hash: '#/' // the "route" to display
};
// render_footer view and append it to the DOM inside the `test-app` node:
document.getElementById(id).appendChild(app.render_footer(model));
// todo-count should display 2 items left (still to be done):
const left = document.getElementById('count').innerHTML;
t.equal(left, "<strong>2</strong> items left", "Todos remaining: " + left);
// count number of footer <li> items:
t.equal(document.querySelectorAll('li').length, 3, "3 <li> in <footer>");
// check footer link text and href:
const link_text = ['All', 'Active', 'Completed'];
const hrefs = ['#/', '#/active', '#/completed'];
document.querySelectorAll('a').forEach(function (a, index) {
// check link text:
t.equal(a.textContent, link_text[index], "<footer> link #" + index
+ " is: " + a.textContent + " === " + link_text[index]);
// check hrefs:
t.equal(a.href.replace('about:blank', ''), hrefs[index],
"<footer> link #" + index + " href is: " + hrefs[index]);
});
// check for "Clear completed" button in footer:
const clear = document.querySelectorAll('.clear-completed')[0].textContent;
t.equal(clear, 'Clear completed', '<button> in <footer> "Clear completed"');
elmish.empty(document.getElementById(id)); // clear DOM ready for next test
t.end();
});
```
Run this test:
```sh
node test/todo-app.test.js
```
you will see something like this:
#### `render_footer` Implementation
Given the docs and test above, attempt to write the `render_footer` function.
> _**Note**: for now we are **not** "concerned"
with what happens when the "Clear completed" **`<buton>`** is clicked/tapped.
We will "cover" that below. For now, focus on rendering the DOM._
> If you get "stuck" trying to make the tests pass, first keep trying! <br />
Then "ask a friend" and finally, consult the _reference_ implementation in:
[**`todo-app.js`**](https://github.com/dwyl/learn-elm-architecture-in-javascript/pull/45/commits/68e2afa3bd95c46da7df559007d90dedcbae500f#diff-6be3e16fe7cfb4c00788d4d587374afdR103)
For good measure, we add a _second_ test to check our "pluarisation":
```js
test('render_footer 1 item left (pluarisation test)', function (t) {
const model = {
todos: [
{ id: 1, title: "Be excellent to each other!", done: false }
],
hash: '#/' // the "route" to display
};
// render_footer view and append it to the DOM inside the `test-app` node:
document.getElementById(id).appendChild(app.render_footer(model));
// todo-count should display "1 item left" (still to be done):
const left = document.getElementById('count').innerHTML;
t.equal(left, "<strong>1</strong> item left", "Todos remaining: " + left);
elmish.empty(document.getElementById(id)); // clear DOM ready for next test
t.end();
});
```
This test _should_ pass without any further code needing to be written.
Once you have written the code to pass the tests,
you should see something like this:
### `view` Function
Now that we have the individual ("_lower order_") functions
**`render_main`**
[#51](https://github.com/dwyl/learn-elm-architecture-in-javascript/issues/51),
**`render_item`**
[#52](https://github.com/dwyl/learn-elm-architecture-in-javascript/issues/52),
and **`render_footer`**
[#53](https://github.com/dwyl/learn-elm-architecture-in-javascript/issues/53)
for rendering the _sections_ of the todo app,
we can write the `view` function to render the _entire_ app!
With the `main` and `footer` "_partial_" views built,
the overall **`view`** is quite simple:
To save on repetition, and illustrate just how _simple_
the **`view`** is,
this is the "HTML" with the
**`<section class"main">`** and **`<footer class="footer">`**
partials replaced by invocations
to the respective functions
**`render_main`** and **`render_footer`**:
```html
<section class="todoapp">
<header class="header">
<h1>todos</h1>
<input class="new-todo" placeholder="What needs to be done?" autofocus="">
</header>
render_main(model)
render_footer(model)
</section>
```
#### `view` Acceptance Criteria
The `view` displays:
+ [ ] **`<section class="todo-app">`** inside which the app is rendered.
+ [ ] **`<h1>`** containing the title text "**todos**".
+ [ ] **`<input class="new-todo">`**
has placeholder text **"What needs to be done?"**
+ [ ] **`<ul class="todo-list">`** list of todo items
has `zero` items by default (_based on the `initial_model`_)
+ [ ] `<footer>` count is Zero when the app is first
rendered with no todos in the `model`.
#### `view` JSDOC Comment Documentation
Here is a sample JSDOC comment you can add to your **`todo-app.js`** file:
```js
/**
* `view` renders the entire Todo List App
* which contains count of items to (still) to be done and a `<ul>` "menu"
* with links to filter which todo items appear in the list view.
* @param {Object} model - the App's (current) model (or "state").
* @return {Object} <section> DOM Tree which containing all other DOM elements.
* @example
* // returns <section class="todo-app"> DOM element with other DOM els nested:
* var DOM = view(model);
*/
```
These should be pretty familiar to you by now.
If you feel comfortable extending it with more detail, go for it!
#### `view` _Tests_
A sample test for the `view` function
you can add to your `test/todo-app.test.js` file:
(_if you feel confident in your TDD skills,
you could **`try`** to write your own test/assertions..._)
```js
test.only('view renders the whole todo app using "partials"', function (t) {
// render the view and append it to the DOM inside the `test-app` node:
document.getElementById(id).appendChild(app.view(app.model)); // initial_model
t.equal(document.querySelectorAll('h1')[0].textContent, "todos", "<h1>todos");
// placeholder:
const placeholder = document.getElementById('new-todo')
.getAttribute("placeholder");
t.equal(placeholder, "What needs to be done?", "paceholder set on <input>");
// todo-count should display "0 items left" (based on initial_model):
const left = document.getElementById('count').innerHTML;
t.equal(left, "<strong>0</strong> items left", "Todos remaining: " + left);
elmish.empty(document.getElementById(id)); // clear DOM ready for n