How to process POST data in Node js

Question

How do you extract form data  form method  post    and file uploads sent from the HTTP POST method in Node js   I ve read the documentation  googled and found nothing   function  request  response          request post         Is there a library or a hack

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If it involves a file upload  the browser usually send it as a  multipart form-data  content-type  You can use this in such cases  var multipart   require  multipart    multipart parse req      Reference 1  Reference 2

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I found a video which explains on how to achieve this  https   www youtube com watch v nuw48-u3Yrg  It uses default  http  module together with  querystring  and  stringbuilder  modules   The application takes two numbers  using two textboxes  from a web page and upon submit  returns sum of those two  along with persisting the values in the textboxes    This is the best example I could find anywhere else   Related source code   var http   require  http    var qs   require  querystring    var StringBuilder   require  stringbuilder     var port   9000   function getCalcHtml req  resp  data        var sb   new StringBuilder   newline    r n          sb appendLine   lt html gt         sb appendLine    lt body gt         sb appendLine        lt form method  post  gt         sb appendLine            lt table gt         sb appendLine                lt tr gt         sb appendLine                    lt td gt Enter First No   lt  td gt          if  data  amp  amp  data txtFirstNo            sb appendLine                    lt td gt  lt input type  text  id  txtFirstNo  name  txtFirstNo  value   0    gt  lt  td gt    data txtFirstNo             else           sb appendLine                    lt td gt  lt input type  text  id  txtFirstNo  name  txtFirstNo    gt  lt  td gt                sb appendLine                lt  tr gt         sb appendLine                lt tr gt         sb appendLine                    lt td gt Enter Second No   lt  td gt          if  data  amp  amp  data txtSecondNo            sb appendLine                    lt td gt  lt input type  text  id  txtSecondNo  name  txtSecondNo  value   0    gt  lt  td gt    data txtSecondNo             else           sb appendLine                    lt td gt  lt input type  text  id  txtSecondNo  name  txtSecondNo    gt  lt  td gt                sb appendLine                lt  tr gt         sb appendLine                lt tr gt         sb appendLine                    lt td gt  lt input type  submit  value  Calculate    gt  lt  td gt         sb appendLine                lt  tr gt          if  data  amp  amp  data txtFirstNo  amp  amp  data txtSecondNo            var sum   parseInt data txtFirstNo    parseInt data txtSecondNo           sb appendLine                lt tr gt             sb appendLine                    lt td gt Sum   0  lt  td gt    sum           sb appendLine                lt  tr gt                sb appendLine            lt  table gt         sb appendLine        lt  form gt        sb appendLine    lt  body gt         sb appendLine   lt  html gt         sb build function  err  result            resp write result           resp end               function getCalcForm req  resp  data        resp writeHead 200     Content-Type    text html          getCalcHtml req  resp  data      function getHome req  resp        resp writeHead 200     Content-Type    text html          resp write   lt html gt  lt html gt  lt head gt  lt title gt Home lt  title gt  lt  head gt  lt body gt Want to some calculation  Click  lt a href   calc  gt here lt  a gt  lt  body gt  lt  html gt         resp end       function get404 req  resp        resp writeHead 404   Resource Not Found      Content-Type    text html          resp write   lt html gt  lt html gt  lt head gt  lt title gt 404 lt  title gt  lt  head gt  lt body gt 404  Resource not found  Go to  lt a href     gt Home lt  a gt  lt  body gt  lt  html gt         resp end       function get405 req  resp        resp writeHead 405   Method not supported      Content-Type    text html          resp write   lt html gt  lt html gt  lt head gt  lt title gt 405 lt  title gt  lt  head gt  lt body gt 405  Method not supported lt  body gt  lt  html gt         resp end       http createServer function  req  resp        switch  req method            case  GET               if  req url                            getHome req  resp                             else if  req url       calc                     getCalcForm req  resp                             else                   get404 req  resp                             break          case  POST               if  req url       calc                     var reqBody                       req on  data   function  data                        reqBody    data                      if  reqBody length  gt  1e7      10MB                         resp writeHead 413   Request Entity Too Large      Content-Type    text html                              resp end   lt  doctype html gt  lt html gt  lt head gt  lt title gt 413 lt  title gt  lt  head gt  lt body gt 413  Request Entity Too Large lt  body gt  lt  html gt                                                               req on  end   function                          var formData   qs parse reqBody                       getCalcForm req  resp  formData                                                 else                   get404 req  resp                             break          default              get405 req  resp               break           listen port

User · Answer

You can use the express middleware  which now has body-parser built into it  This means all you need to do is the following   import express from  express   const app   express    app use express json     app post   thing    req  res    gt      console log req body      lt -- this will access the body of the post   res sendStatus 200       That code example is ES6 with Express 4 16 x

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Make sure to kill the connection if someone tries to flood your RAM   var qs   require  querystring     function  request  response        if  request method     POST             var body               request on  data   function  data                body    data                 1e6     1   Math pow 10  6      1   1000000     1MB             if  body length  gt  1e6                        FLOOD ATTACK OR FAULTY CLIENT  NUKE REQUEST                 request connection destroy                                      request on  end   function                   var POST   qs parse body                  use POST

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You can use body-parser  the Node js body parsing middleware   First load body-parser     npm install body-parser --save   Some example code  var express   require  express   var bodyParser   require  body-parser    var app   express    app use bodyParser urlencoded   extended  false     app use bodyParser json      app use function  req  res      var post data   req body    console log post data        More documentation can be found here

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You need to receive the POST data in chunks using request on  data   function chunk          const http   require  http     http createServer  req  res    gt        if  req method     POST             whole              req on  data    chunk    gt                  consider adding size limit here             whole    chunk toString                       req on  end        gt                console log whole              res writeHead 200   OK     Content-Type    text html                res end  Data received                        listen 8080    You should consider adding a size limit at the indicated position as thejh suggested

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If you use Express  high-performance  high-class web development for Node js   you can do this   HTML    lt form method  post  action     gt       lt input type  text  name  user name   gt       lt input type  text  name  user email   gt       lt input type  submit  value  Submit  gt   lt  form gt    API client   fetch            method   POST       headers             Content-Type    application json             body  JSON stringify           user                name   John               email   john example com                         Node js   since Express v4 16 0      Parse URL-encoded bodies  as sent by HTML forms  app use express urlencoded         Parse JSON bodies  as sent by API clients  app use express json         Access the parse results as request body app post      function request  response       console log request body user name       console log request body user email         Node js   for Express  lt 4 16 0   const bodyParser   require  body-parser         bodyParser urlencoded options     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     app use bodyParser urlencoded       extended  true          bodyParser json options     Parses the text as JSON and exposes the resulting object on req body      app use bodyParser json      app post      function  req  res        console log req body user name

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If you are using Express js  before you can access to the req body  you must add middleware bodyParser   app use express bodyParser       Then you can ask for  req body user

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Limit POST size avoid flood your node app  There is a great raw-body module  suitable both for express and connect  that can help you limit request by size and length

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If you prefer to use pure Node js then you might extract POST data like it is shown below    x000D   x000D     Dependencies x000D  const StringDecoder   require  string decoder   StringDecoder  x000D  const http   require  http    x000D   x000D     Instantiate the HTTP server  x000D  const httpServer   http createServer  request  response    gt    x000D       Get the payload  if any  x000D    const decoder   new StringDecoder  utf-8    x000D    let payload       x000D   x000D    request on  data    data    gt    x000D      payload    decoder write data   x000D        x000D   x000D    request on  end        gt    x000D      payload    decoder end    x000D   x000D         Parse payload to object  x000D      payload   JSON parse payload   x000D   x000D         Do smoething with the payload     x000D        x000D     x000D   x000D     Start the HTTP server  x000D  const port   3000  x000D  httpServer listen port       gt    x000D    console log  The server is listening on port   port     x000D      x000D   x000D   x000D

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You can use the querystring module   var qs   require  querystring     function  request  response        if  request method     POST             var body                request on  data   function  data                body    data                  Too much POST data  kill the connection                 1e6     1   Math pow 10  6      1   1000000     1MB             if  body length  gt  1e6                  request connection destroy                         request on  end   function                  var post   qs parse body                  use post  blah    etc                        Now  for example  if you have an input field with name age  you could access it using the variable post   console log post age

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Reference  https   nodejs org en docs guides anatomy-of-an-http-transaction    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

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ONE LINER without MIDDLEWARE  If you post following data   name   ABC  Then you can parse it using the following one liner    require  url   parse req url  true  query name

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Express v4 17 0  app use express urlencoded   extended  true      console log req body     object  Demo Form Another Answer Related

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1  Install  body-parser  from npm   2  Then in your app ts   var bodyParser   require  body-parser      3  then you need to write   app use bodyParser json      in app ts module  4  keep in mind that you include   app use bodyParser json      in the top or before any module declaration   Ex    app use bodyParser json    app use   user  user     5  Then use   var postdata   req body

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You can easily send and get the response of POST request by using  Request - Simplified HTTP client  and Javascript Promise       var request   require  request     function getData         var options             url   https   example com           headers                 Content-Type    application json                        return new Promise function  resolve  reject            var responseData          var req   request post options   err  res  body    gt                if  err                    console log err                   reject err                 else                   console log  Responce Data   JSON parse body                    responseData   body                  resolve responseData

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It will be cleaner if you encode your data to JSON  then send it to Node js   function  req  res        if  req method     POST             var jsonString                req on  data   function  data                jsonString    data                       req on  end   function                  console log JSON parse jsonString

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There are multiple ways to do it  However  the quickest way I know is to use the Express js library with body-parser   var express   require  express    var bodyParser   require  body-parser    var app   express     app use bodyParser urlencoded  extended   true      app post   pathpostdataissentto   function request  response      console log request body       Or   console log request body fieldName        app listen 8080     That can work for strings  but I would change bodyParser urlencoded to bodyParser json instead if the POST data contains a JSON array   More info  http   www kompulsa com how-to-accept-and-parse-post-requests-in-node-js

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Here s a very simple no-framework wrapper based on the other answers and articles posted in here   var http   require  http    var querystring   require  querystring     function processPost request  response  callback        var queryData           if typeof callback      function   return null       if request method     POST             request on  data   function data                queryData    data              if queryData length  gt  1e6                    queryData                       response writeHead 413    Content-Type    text plain    end                    request connection destroy                                       request on  end   function                 request post   querystring parse queryData               callback                       else           response writeHead 405    Content-Type    text plain             response end              Usage example   http createServer function request  response        if request method     POST             processPost request  response  function                 console log request post                  Use request post here              response writeHead 200   OK     Content-Type    text plain                 response end                      else           response writeHead 200   OK     Content-Type    text plain             response end              listen 8000

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you can extract post parameter without using express    1  nmp  install multiparty  2   import multiparty   as var multiparty   require  multiparty     3     if req method     POST       var form   new multiparty Form       form parse req  function err  fields  files          console log fields  userfile1   0                    4  and HTML FORM IS      lt form method POST enctype multipart form-data gt   lt input type text name userfile1 gt  lt br gt   lt input type submit gt   lt  form gt    I hope this will work for you  Thanks

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A lot of answers here are not good practices anymore or don t explain anything  so that s why I m writing this   Basics  When the callback of http createServer is called  is when the server have actually received all the headers for the request  but it s possible that the data have not been received yet  so we have to wait for it  The http request object a http IncomingMessage instance  is actually a readable stream  In readable streams whenever a chunk of data arrives  a data event is emitted assuming you have registered a callback to it  and when all chunks have arrived an end event is emitted  Here s an example on how you listen to the events    http createServer  request  response    gt      console log  Now we have a http message with headers but no data yet       request on  data   chunk   gt        console log  A chunk of data has arrived     chunk           request on  end        gt        console log  No more data            listen 8080    Converting Buffers to Strings  If you try this you will notice the chunks are buffers  If you are not dealing with binary data and need to work with strings instead I suggest use request setEncoding method which causes the stream emit strings interpreted with the given encoding and handles multi-byte characters properly   Buffering Chunks  Now you are probably not interested in each chunk by it s own  so in this case probably you want to buffer it like this   http createServer  request  response    gt      const chunks         request on  data   chunk   gt  chunks push chunk      request on  end        gt        const data   Buffer concat chunks       console log  Data     data           listen 8080    Here Buffer concat is used  which simply concatenates all buffers and return one big buffer  You can also use the concat-stream module which does the same   const http   require  http    const concat   require  concat-stream    http createServer  request  response    gt      concat request  data   gt        console log  Data     data            listen 8080    Parsing Content  If you are trying to accept HTML forms POST submission with no files or handing jQuery ajax calls with the default content type  then the content type is application x-www-form-urlencoded with uft-8 encoding  You can use the querystring module to de-serialize it and access the properties   const http   require  http    const concat   require  concat-stream    const qs   require  querystring    http createServer  request  response    gt      concat request  buffer   gt        const data   qs parse buffer toString         console log  Data     data            listen 8080    If your content type is JSON instead  you can simply use JSON parse instead of qs parse   If you are dealing with files or handling multipart content type  then in that case  you should use something like formidable which removes all the pain from dealing with it  Have a look at this other answer of mine where I have posted helpful links and modules for multipart content   Piping  If you don t want to parse the content but rather pass it to somewhere else  for example send it to another http request as the data or save it to a file I suggest piping it rather than buffering it  as it ll be less code  handles back pressure better  it ll take less memory and in some cases faster   So if you want to save the content to a file    http createServer  request  response    gt       request pipe fs createWriteStream    request         listen 8080    Limiting the Amount of Data  As other answers have noted keep in my mind that malicious clients might send you a huge amount of data to crash your application or fill your memory so to protect that make sure you drop requests which emit data pass a certain limit  If you don t use a library to handle the incoming data  I would suggest using something like stream-meter which can abort the request if reaches the specified limit   limitedStream   request pipe meter 1e7    limitedStream on  data         limitedStream on  end           or   request pipe meter 1e7   pipe createWriteStream          or   concat request pipe meter 1e7            NPM Modules  While I described above on how you can use the HTTP request body  for simply   buffering and parsing the content  I suggesting using one of these modules rather implementing on your own as they will probably handle edge cases better  For express I suggest using body-parser  For koa  there s a similar module   If you don t use a framework  body is quite good

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If you don t want to chunk your data together with the data callback you can always use the readable callback like this      Read Body when Available request on  readable   function      request body         while  null      request body    request read               Do something with it request on  end   function      request body   - gt  POST Parameters as String       This approach modifies the incoming request  but as soon as you finish your response the request will be garbage collected  so that should not be a problem   An advanced approach would be to check the body size first  if you re afraid of huge bodies

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For anyone wondering how to do this trivial task without installing a web framework I managed to plop this together  Hardly production ready but it seems to work   function handler req  res        var POST           if  req method     POST             req on  data   function data                data   data toString                data   data split   amp                 for  var i   0  i  lt  data length  i                      var  data   data i  split                       POST  data 0      data 1                             console log POST

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And if you don t want to use the entire framework like Express  but you also need different kinds of forms  including uploads  then formaline may be a good choice   It is listed in Node js modules

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Here is how you can do it if you use node-formidable   var formidable   require  formidable     var form   new formidable IncomingForm    form parse request  function  err  fields        console log fields parameter1       console log fields parameter2

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On form fields like these       lt input type  text  name  user name   value  MyName  gt      lt input type  text  name  user email   value  myemail somewherefarfar com  gt    some of the above answers will fail because they only support flat data   For now I am using the Casey Chu answer but with the  qs  instead of the  querystring  module  This is the module  body-parser  uses as well  So if you want nested data you have to install qs    npm install qs --save   Then replace the first line like     var qs   require  querystring    var qs   require  qs      function  request  response        if  request method     POST             var body                request on  data   function  data                body    data                  Too much POST data  kill the connection                 1e6     1   Math pow 10  6      1   1000000     1MB             if  body length  gt  1e6                  request connection destroy                         request on  end   function                  var post   qs parse body               console log post user name      should work                use post  blah    etc

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For those using raw binary POST upload without encoding overhead you can use   client   var xhr   new XMLHttpRequest    xhr open  POST     api upload   true   var blob   new Uint8Array  65 72 79 74       or e g  recorder getBlob   xhr send blob     server   var express   require  express    var router   express Router    var fs   require  fs     router use  function req  res  next      var data       req setEncoding  binary      req on  data   function chunk        data    chunk           req on  end   function         req body   data      next               router post   api upload   function req  res  next      fs writeFile  binaryFile png   req body   binary   function err        res send  Binary POST successful

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You need to use bodyParser   if you want the form data to be available in req body  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

[node.js] How to process POST data in Node.js?

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