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Express Basics

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The Request Object

4:29 with Andrew Chalkley and Joel Kraft

A closer look at Express's Request object.

A note on body-parser

If you are following along with the same version of Express installed in this course (v4.15.2), you should have no problems with using body-parser here. However, if you are using a more recent version of Express (v4.16.0 or higher) you will only need to use the following at the beginning of your document: app.use(express.urlencoded());.

You can read more about this newer built-in middleware in the Express Documentation

HTML Forms

Documentation

What body-parser Does Under the Hood

What is body-parser doing? In case you're curious, here's a little code that reads the body of an incoming request and logs it to the console. This is just a flavor of how using body-parser is making your life easier!

  let bodyString = ''
  req.on('data', chunk => bodyString += chunk.toString());
  req.on('end', () => {
    console.log(bodyString);
  });

Note that even after bodyString has been read completely, it still needs to be turned from a string into data your application can use, all of which is taken care of by body-parser.

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    Remember when we wrote out first route by hand and had to use a request and 0:00
    response object for the route handler. 0:05
    We've been using the response object to return a response to the client. 0:08
    But we haven't been using the request object yet, apart from declaring it. 0:12
    Let's look at the express documentation for the request object. 0:18
    There are quite a few properties that you can access on the request. 0:22
    The one we're most interested in is the body property. 0:28
    This is where our form response will end up. 0:33
    Notice though, that by default it is undefined. 0:36
    To put the form responses into the body, we'll need what is called Middleware. 0:41
    Middleware is basically some code that fits in the middle of a request or 0:47
    a response. 0:51
    Middleware does something to the incoming data and 0:53
    hands the result of to the rest of your application. 0:56
    We'll look more deeply at Middleware later in this course. 1:00
    But we don't really need to know a lot about it yet. 1:04
    I will show you how to install some middleware in a moment. 1:06
    First, though, 1:10
    let's use the console to take a look at the request object more closely. 1:11
    In the app.js file, 1:16
    I'll add a line in the post route to print out the request object to the console. 1:19
    I'll save it and then go back to the browser to create a new request. 1:25
    Our code will run. 1:31
    I don't need a name right now, and I'll click on Submit. 1:34
    Moving to the console where Express is running, 1:39
    you can see that the request object includes a lot of information. 1:41
    We will look too closely at the request. 1:46
    I just wanted you to get an appreciation for 1:48
    the amount of work expressed as to simplify our job as developers. 1:51
    Most of the time, we don't need many of these properties. 1:56
    We'll just access a select few. 1:58
    I'll clear this screen, and then we'll switch back to the app.js file. 2:02
    I'm just going to examine the body property now. 2:06
    If I submit the form now using my name And switch to the console, 2:11
    as you can see, I get undefined, just as the documents promised. 2:19
    Let's install the middleware, called for by the docs. 2:25
    It's called body parser and it will process the incoming form submission data 2:30
    into a format that's easier for our program to read. 2:34
    I'll go to the terminal and then I'll type, 2:39
    npm install body-parser. 2:45
    When that's done, I can require it in my app.js file at the top. 2:51
    Now, we'll tell Express to use it. 3:09
    Body-parser contains several parses, the different ways the clients can send data. 3:12
    HTML forms normally encode the data they send the same way URLs do. 3:19
    So, we'll need to use the urlencode parser. 3:25
    We'll pass in an object, turning 3:32
    off the parser's extended option. 3:37
    Don´t worry too much about this line of code. 3:46
    To be honest, 3:49
    I have to look this up everytime I need to include it in my Express applications. 3:50
    I've included more information about how forms and data and 3:56
    how body-parser works in the teacher's notes. 3:59
    Now, let's submit a name. 4:03
    In the console, you can see the body property has now a username property. 4:06
    Our app is now able to understand the information it's getting from our form. 4:14
    Next, we'll use that information to send something meaningful back to the client. 4:19
    While we do this, let's take a closer look at the response objects in the next video. 4:24

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