01 Lab 1 Templates and Forms.md

The ECMA6 Programming Language

Supporting resources:

1. ECMA6 presentation

In this lab you will get to grips with the ECMA6 programming language by learning to build dynamic websites

1 Templating

We will start by producing dynamic web pages that combine a static layout with dynamic data using a templating view engine.

There are a number of templating view engines that are compatible with Express however in this worksheet we will be using one of the more popular ones, called Handlebars. This needs to be imported into your script and set the default layout page.

Each lab exercise is based on files located in the exercises/ directory. The structure of this mirrors that of the topics and labs. For this part of the lab you will be working with the same lab files you used in the setup exercise.

1. As you have already seen, this displays a simple message together with the picture of a clock.
2. Add /date to the end of the URL, notice that this now displays a page showing the current date.
3. Finally replace the /date with /food, again notice you are viewing a different page, this time listing some different foods.

By changing the URL you tell the server to send you different web pages. This is how the World-Wide-Web works. The bit of text after the server name and port is known as the route. Open the index.js file and study the script, can you see how it is serving up the three different pages?

1.1 Basic Templating

The URL without any additions is called the base route, and is shown with a /. Locate the app.get() function that handles this route.

1. We start by importing the Handlebars package and create a default layout called main. This defines the main.handlebars page as the one to use as the default website layout.
   1. Open the views/layouts/main.handlebars file.
   2. This template page will be used by all the pages in the website.
   3. Notice there is a {{{body}}} placeholder, this defines where the different page templates will be inserted.
2. In the base route / we call the res.render() function and pass it the name of the template we want to use:
   1. The parameter is a string, home.
   2. This refers to the template views/home.handlebars
3. The contents of the home.handebars template is inserted into the layout file replacing the {{{body}}} placeholder.

1.1.1 Static Files

When an html page is loaded into a browser it contains link to other static files such as stylesheets and images. These need to be stored in a directory on the Express server which is visible to the browser:

1. Open the index.js script and locate line 11, this tells the Express web server to make the contents of the public/ directory visible to external clients.
2. Locate the public/ directory and notice it contains two directories
   1. One called css/ containing the stylesheet
   2. And one called images/ containing some image files.
3. Because all the pages share the same stylesheet, the views/layouts/main.handlebars file includes a link to the stylesheet.
4. We have also added an img element to the home.handlebars html to display the image.

1.1.2 Test Your Understanding

1. Create a /hello route that uses a template file called hello.handlebars to display a heading with the text Hello World!
2. Modify the external stylesheet to display the heading in dark red.
3. Find a smiley face image online and display this on the page.

1.2 Inserting Data into a Template

So far we have not done anything particularly useful except separate out the layout from the content. In this section you will learn how to insert data directly into a template before it is rendered to the browser.

In the previous example you have seen how to insert single values into a web page but how to we display lists of data? A list is stored in an array in JavaScript so the first task is to ensure your data is in an array. If you are not sure, make use of the console.log() function to print data to the terminal window.

Restart the server and access the /date route. Notice that it displays the current date in the browser. Open the index.js file and locate the route.

1. We start by creating a new Date object.
2. We use its built-in functions to create a string containing the current date.
3. Next we create a JavaScript object that contains all the data we want to send to the template:
   1. In this example we have a title property containing the string My First Template.
   2. We have a seccond property called today that contains the date string we have just built.
4. Finally we call res.render() but this time we pass the data as the second parameter.

To understand what happens to this data we need to understand the template. Locate the views/date.handlebars template file:

1. Notice that there are two placeholders, shown as {{xxx}}.
   1. Each placeholder has a name.
   2. The names need to match the properties in the data we are sending to the template.
2. Each placeholder is replaced by the data stored against the object property:
   1. The {{title}} placeholder is replaced by the string My First Template.
   2. The {{date}} placeholder is replaced with the date string we built in the script.

There are two forms of the placeholder, one uses double brackets {{xxx}} and the other triple brackets {{{xxx}}}. The only difference is how the inserted data is processed. With double braces, the data is URL-Encoded before being inserted. This replaces 'illegal' characters such as < and & with their codes. If your data contains html elements such as <p>, you will find these display in the web page instead of being treated as markup. You can see this by right-clicking in the browser and choosing View page source.

1.2.1 Test Your Understanding

You will now modify the /date route as follows:

1. Use suitable properties of the Date object to add paragraph elements to display the following:
   1. The current time in the 24 hour time format: HH:MM:SS
   2. a Unix timestamp (number of seconds since 1st Jan 1970)
2. Insert a picture of a calendar.

1.3 Repeating Data

So far we have inserted data from object properties into our templates. This works find for single records however often we will have multiple records to display such as the results of a database query. In this situation we will need to repeat a block of html code such as a list item or table row.

Restart the server and view the /food route. Notice that it displays a numbered list showing four food items. Locate the route in your script.

1. We start by creating an array. Each imdex contains an object with two properties, name and qty.
2. We pass the array to res.render() as a JavaScript object using the myFood property.

Open the food.handlebars template:

1. Notice that there is an ordered list element.
2. Inside this there is a special helper, {{#each myFood}}
   1. The helper also has a closing block {{/each}}
   2. The myFood property is passed to the opening block.
3. This block loops through the array stored in the myFood property.
4. The this object holds the object for the current index.
   1. So this.item returns the item property (the name of the food item).

This allows the handlebars template view engine to handle repeated data.

1.3.1 Test Your Understanding

1. Modify the template to display the shopping items in a html table instead of an ordered list.
2. Add a second column to display the quantities of each item.
3. Add a table header to display column headings.
4. Without adding any more html, colour every other row of the table in light grey.

2 Forms

In this final part of the worksheet you will be building forms that can send data to a web server. Locate the simple_forms/ directory, install the necessary modules and start the server.

Lets start by looking at how forms send data to the server. This can be done using the HTTP GET method or using the POST method. Lets try out both so we can understand the differences.

2.1 Submitting Data Using POST

Make sure the web server is running and access the /postform route and open the corresponding html file.

1. Complete the form with your name.
2. Click on the the Submit button.
3. Examine the URL carefully:
   1. Notice that it points to the base route / with no additional data in the URL.
4. Open the Chrome developer tools and look at the http request (select the Network tab and click on the URL in the Name column):
   1. Notice that the request uses the POST method. This corresponds to the method attribute in the <form> element.
   2. The request header includes a Content-Type header which contains the value application/x-www-form-urlencoded.
5. There is a request body which contains the form data:
   1. This uses the application/x-www-form-urlencoded encoding.
   2. Notice that it contains 2 query parameters in a querystring.
   3. The names of the query parameters correspond to the values in the name attributes in the <input> elements.

2.1.1 Test Your Understanding

1. Currently all the form data is processed in a loop and added to the table:
   1. Modify the post.handlebars template to display the full name as a second level heading.
2. Add a new field to store an email address

2.2 Submitting Data Using GET

Make sure the web server us running and access the /getform route and open the corresponding html file.

1. Complete the form with your name.
2. Click on the the Submit button.
3. Examine the URL carefully:
   1. Notice that it contains 2 query parameters in a querystring.
   2. The names of the query parameters correspond to the values in the name attributes in the <input> elements.
4. Open the Chrome developer tools and look at the http request:
   1. Notice that the request uses the GET method. This corresponds to the method attribute in the <form> element.
   2. The URL contains the data (remember there is only a request body when the POST method is used.

2.3 Form Controls

In the previous section the form used the <input> element which displayed simple text boxes where you could enter anything. In this section you are going to learn about how to use a wide range of different controls to capture user input.

locate and open the complex_forms/ directory. Install the required modules and start the server. Open the /register route which will display a course registration form, complete this and submit the form. This demonstrates some of the more complex controls you can use. Open the views/register.handlebars file which contains the markup used to render the form. Notice the following (see how many you can spot in the example form):

1. The form is split into several logical sections using the fieldset element.
2. Each fieldset has a legend element that represents its caption.
3. Each form element has a name attribute. This is the key that the data can be accessed from by the processing script. Try completing the form and submitting. Examine the JSON data and compare the object keys to the form element names.
4. Each form element has a label. The for attribute should match the name attribute of the form element it is labelling.
5. The input element defines a number of input types that can be used in forms:
   • Plain text: <input type="text">
   • Password fields: <input type="password">
   • Email addresses: <input type="email">
   • URL addresses: <input type="url">
   • Numeric data: <input type="number">
   • Date pickers: <input type="date">
   • Hidden fields <input type="hidden">
6. Sometimes we want the user to pick from a list of options:
   1. The select element creates a dropdown list with each list item defined as an option
   2. If we set the type attribute of an input element to radio we create a set of radio buttons. If we set the name of each to the same, only one can be selected at once.

2.4.1 Test Your Understanding

Complete the following tasks. After each, complete and submit the form to ensure all data is available:

1. Add a box for the user's email address in the personal detail section.
2. Create a new fieldset for the user's address and add input boxes to capture this. Make sure each box has a unique, descriptive name attribute.
3. You will find a json file containing a longer list of courses. Replace the static list with the data contained in this file (you will need to pass some repeating data to the template).
   1. To load the data from a file you need to use the fs.readfile() function.
   2. You are loading a JSON-formatted string from the file. To turn this into an object you need to use JSON.parse().
   3. You then need to extract the array from the object (try using console.log() to visualise the data.
   4. You then need to pass this array to the handlebars template and insert a helper in this template to insert the courses into the dropdown list.
4. Display the form data on the page rather than just the JSON string (you will need to pass each item through to the template and insert into individual placeholders).
5. Add a link to the data page to return to the form.