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I'm wanting to make an ajax call from the client to the backend. I get a successful call from the success function, however, I can't understand how I get data from the server to return from the client.

currently my error trying to use res.send is:

Error: Can't set headers after they are sent.

AJAX

function getProfessorResults() {
      var textData = $('#inputsm').val();

      var data = {user:"[email protected]"};
      $.ajax({
          url: 'http://localhost:3000',
          data: { theme: "somevalue", snippet: { name: "somename", content: "somevalue" } },
          method: 'POST',
          async: false,
          cache: false,
          timeout: 5000,
          contentType: "application/json",
          success: function(data) {
              console.log("success");
          },
          plete: function(data) {
            console.log("pleted");
          },
          error: function(jqXHR, textStatus, errorThrown) {

              alert('Error connecting to the Node.js server... ' + textStatus + " " + errorThrown);
          }
      });
    }

JS Backend

exports.home = function(req, res) {


  function passList(profArray, callback) {
    setTimeout(function () {
      callback(profArray);
    }, 1000);
  }


  function getProfs(teacher_name, successCallback) {

    google.resultsPerPage = 10
    var nextCounter = 0

    google(teacher_name, function (err, res){
      if (err) console.error(err)
      var teacher_results = []; //Hold all the teachers returned from the function
      for (var i = 0; i < res.links.length; ++i) {
        var link = res.links[i];
        if (!link.title.includes('Add') || !link.title.includes('RATINGS') || !link.title.includes("Hint")) {

            teacher_results.push(link.title);

        }//End if for parisons ||
      } //End For
      successCallback(teacher_results);
    }); //End google function
      teacher_results = ['tester1', 'tester2'];
      successCallback(teacher_results);
  } //End searchForProfessor


  getProfs(teacher_name, function(data) {
    prof_list = data;
    console.log(prof_list);
    return true;
  });


  if (req.method == 'POST'){
      console.log("true");
      // dataReceived = JSON.parse(req);
      // console.log(dataReceived);
      var obj = {
          tid: 'ryan'
      };

      res.send(JSON.stringify(obj));
   }



  res.render('home', {
    profs: prof_list,
    dataStuff : dataReceived
  });
};

I'm wanting to make an ajax call from the client to the backend. I get a successful call from the success function, however, I can't understand how I get data from the server to return from the client.

currently my error trying to use res.send is:

Error: Can't set headers after they are sent.

AJAX

function getProfessorResults() {
      var textData = $('#inputsm').val();

      var data = {user:"[email protected]"};
      $.ajax({
          url: 'http://localhost:3000',
          data: { theme: "somevalue", snippet: { name: "somename", content: "somevalue" } },
          method: 'POST',
          async: false,
          cache: false,
          timeout: 5000,
          contentType: "application/json",
          success: function(data) {
              console.log("success");
          },
          plete: function(data) {
            console.log("pleted");
          },
          error: function(jqXHR, textStatus, errorThrown) {

              alert('Error connecting to the Node.js server... ' + textStatus + " " + errorThrown);
          }
      });
    }

JS Backend

exports.home = function(req, res) {


  function passList(profArray, callback) {
    setTimeout(function () {
      callback(profArray);
    }, 1000);
  }


  function getProfs(teacher_name, successCallback) {

    google.resultsPerPage = 10
    var nextCounter = 0

    google(teacher_name, function (err, res){
      if (err) console.error(err)
      var teacher_results = []; //Hold all the teachers returned from the function
      for (var i = 0; i < res.links.length; ++i) {
        var link = res.links[i];
        if (!link.title.includes('Add') || !link.title.includes('RATINGS') || !link.title.includes("Hint")) {

            teacher_results.push(link.title);

        }//End if for parisons ||
      } //End For
      successCallback(teacher_results);
    }); //End google function
      teacher_results = ['tester1', 'tester2'];
      successCallback(teacher_results);
  } //End searchForProfessor


  getProfs(teacher_name, function(data) {
    prof_list = data;
    console.log(prof_list);
    return true;
  });


  if (req.method == 'POST'){
      console.log("true");
      // dataReceived = JSON.parse(req);
      // console.log(dataReceived);
      var obj = {
          tid: 'ryan'
      };

      res.send(JSON.stringify(obj));
   }



  res.render('home', {
    profs: prof_list,
    dataStuff : dataReceived
  });
};

• javascript
• jquery
• ajax
• node.js

Share Improve this question Follow edited May 14, 2016 at 17:49 CuriousFellow asked May 14, 2016 at 17:22 CuriousFellowCuriousFellow 21511 gold badge33 silver badges1414 bronze badges 5

• return to where? Need to know more about server code context – charlietfl Commented May 14, 2016 at 17:32
• Say I call a method on the server-side. I want the data from the server to return, say a string of data or JSON obj, back to the client so I can throw it onto my template. – CuriousFellow Commented May 14, 2016 at 17:34
• You need to include more of your JS Backend code. – JAM Commented May 14, 2016 at 17:46
• @JAM updated the original – CuriousFellow Commented May 14, 2016 at 17:49
• I think error occurred because you call res.render after res.send. – Sergii Shvager Commented May 14, 2016 at 17:53

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2 Answers 2

Sorted by: Reset to default 4

In the backend, you should have some route where your AJAX call lands. In there, you can invoke send on your response.

In node.js/express, this would look something like

app.get('/ajaxURL', function (req, res) {
  res.send('I want this string to return to the client');
});

To access the data from the frontend, access it in your AJAX callback:

$.ajax({url: '/ajaxURL'}).done(function (data) {
    console.log(data);
});

I am not getting the context properly but you can figure out by this example .

Sending data from server response.send("Your data"); Access this data in your client in success method of AJAX: success:function(data){console.log(data)};

本文标签： javascriptAJAX call and getting return data in NodeStack Overflow