What does body-parser do with express

Question

I don t understand why we need body-parser in an Express application  as we can get data without using body-parser  And what does it do actually and how

User · Answer

To handle HTTP POST request in Express js version 4 and above  you need to install middleware module called body-parser    body-parser extract the entire body portion of an incoming request stream and exposes it on req body    The middleware was a part of Express js earlier but now you have to install it separately   This body-parser module parses the JSON  buffer  string and URL encoded data submitted using HTTP POST request  Install body-parser using NPM as shown below   npm install body-parser --save   edit in 2019-april-2  in express 4 16 0 the body-parser middleware bundled with express  for more details see this

User · Answer

Understanding Requests Body     When receiving a POST or PUT request  the request body might be   important to your application  Getting at the body data is a little   more involved than accessing request headers  The request object   that s passed in to a handler implements the ReadableStream interface    This stream can be listened to or piped elsewhere just like any other   stream  We can grab the data right out of the stream by listening to   the stream s  data  and  end  events       The chunk emitted in each  data  event is a Buffer  If you know it s   going to be string data  the best thing to do is collect the data in   an array  then at the  end   concatenate and stringify it   let body       request on  data    chunk    gt      body push chunk      on  end        gt      body   Buffer concat body  toString         at this point   body  has the entire request body stored in it as a string        Understanding body-parser   As per its documentation     Parse incoming request bodies in a middleware before your handlers    available under the req body property    As you saw in the first example  we had to parse the incoming request stream manually to extract the body  This becomes a tad tedious when there are multiple form data of different types  So we use the body-parser package which does all this task under the hood   It provides four modules to parse different types of data   JSON body parser Raw body parser Text body parser URL-encoded form body parser   After having the raw content body-parser will use one of the above strategies depending on middleware you decided to use  to parse the data  You can read more about them by reading their documentation    After setting the req body to the parsed body  body-parser will invoke next   to call the next middleware down the stack  which can then access the  request data without having to think about how to unzip and parse it

User · Answer

Keep it simple    if you used post so you will need the body of the request  so you will need body-parser   No need to install body-parser with express  but you have to use it if you will receive post request  app use bodyParser urlencoded   extended  false        extended  false   false meaning  you do not have nested data inside your body object  Note that  the request data embedded within the request as a body Object

User · Answer

If you don t want to use seperate npm package body-parser  latest express  4 16   has built-in body-parser middleware and can be used like this  const app   express    app use express json   limit   100mb        p s  Not all functionalities of body parse are present in the express  Refer documentation for full usage here

User · Answer

It parses the HTTP request body  This is usually necessary when you need to know more than just the URL you hit  particular in the context of a POST or PUT PATCH HTTP request where the information you want is contains in the body   Basically its a middleware for parsing JSON  plain text  or just returning a raw Buffer object for you to deal with as you require

User · Answer

Let   s try to keep this least technical   Let   s say you are sending a html form data to node-js server i e  you made a request to the server  The server file would receive your request under a request object  Now by logic  if you console log this request object in your server file you should see your form data some where in it  which could be extracted then  but whoa   you actually don   t    So  where is our data   How will we extract it if its not only present in my request   Simple explanation to this is http sends your form data in bits and pieces which are intended to get assembled as they reach their destination  So how would you extract your data   But  why take this pain of every-time manually parsing your data for chunks and assembling it  Use something called    body-parser    which would do this for you   body-parser parses your request and converts it into a format from which you can easily extract relevant information that you may need   For example  let   s say you have a sign-up form at your frontend  You are filling it  and requesting server to save the details somewhere   Extracting username and password from your request goes as simple as below if you use body-parser   var loginDetails             username   request body username          password   request body password          So basically  body-parser parsed your incoming request  assembled the chunks containing your form data  then created this body object for you and filled it with your form data

User · Answer

These are all a matter of convenience   Basically  if the question were  Do we need to use body-parser   The answer is  No   We can come up with the same information from the client-post-request using a more circuitous route that will generally be less flexible and will increase the amount of code we have to write to get the same information    This is kind of the same as asking  Do we need to use express to begin with   Again  the answer there is no  and again  really it all comes down to saving us the hassle of writing more code to do the basic things that express comes with  built-in    On the surface - body-parser makes it easier to get at the information contained in client requests in a variety of formats instead of making you capture the raw data streams and figuring out what format the information is in  much less manually parsing that information into useable data

User · Answer

In order to get access to the post data we have to use body-parser  Basically what the body-parser is which allows express to read the body and then parse that into a Json object that we can understand

User · Answer

Yes we can work without body-parser  When you don t use that you get the raw request  and your body and headers are not in the root object of request parameter   You will have to individually manipulate all the fields   Or you can use body-parser  as the express team is maintaining it    What body-parser can do for you  It simplifies the request  How to use it  Here is example   Install npm install body-parser --save  This how to use body-parser in express   const express   require  express          app   express          bodyParser   require  body-parser        support parsing of application json type post data app use bodyParser json        support parsing of application x-www-form-urlencoded post data app use bodyParser urlencoded   extended  true        Link   https   github com expressjs body-parser   And then you can get body and headers in root request object   Example  app post   posturl  function req res next       console log req body       res send  response

User · Answer

The answer here explain it very detailed and brilliantly  the answer contains   In short  body-parser extracts the entire body portion of an incoming request stream and exposes it on req body as something easier to interface with  You don t need it per se  because you could do all of that yourself  However  it will most likely do what you want and save you the trouble   To go a little more in depth  body-parser gives you a middleware which uses nodejs zlib to unzip the incoming request data if it s zipped and stream-utils raw-body to await the full  raw contents of the request body before  quot parsing it quot   this means that if you weren t going to use the request body  you just wasted some time   After having the raw contents  body-parser will parse it using one of four strategies  depending on the specific middleware you decided to use   bodyParser raw    Doesn t actually parse the body  but just exposes the buffered up contents from before in a Buffer on req body   bodyParser text    Reads the buffer as plain text and exposes the resulting string on req body   bodyParser urlencoded    Parses the text as URL encoded data  which is how browsers tend to send form data from regular forms set to POST  and exposes the resulting object  containing the keys and values  on req body  For comparison  in PHP all of this is automatically done and exposed in   POST   bodyParser json    Parses the text as JSON and exposes the resulting object on req body    Only after setting the req body to the desirable contents will it call the next middleware in the stack  which can then access the request data without having to think about how to unzip and parse it   You can refer to body-parser github to read their documentation  it contains information regarding its working

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