Request callback with node

Question

I'm trying to create a callback function, but keep getting told that data is not a function. I've set it up according to another question, but does not seem to work?

getRequest("http://", function(error, data){
  console.log(data);
});

function getRequest(url, error, data) {
  request({
      method: 'GET',
      uri: url,
      headers: {
        'Content-Type': 'application/json',
        'dataType': 'json'}
    }, function (error, response, body){
      if(!error && response.statusCode == 200){

        data(JSON.parse(body));

      } else {
        error(error);
      }
    })
}

You are calling getRequest with two params. so the third data param is undefined. — Roland Starke
– Roland Starke, Commented Sep 5, 2016 at 11:20
You might want to consider using a promise library like Bluebird to keep your callbacks under control. Chaining then(...) is often a lot easier than matching up function calls. — tadman
– tadman, Commented Sep 5, 2016 at 12:04

G07cha · Accepted Answer · 2016-09-05 11:58:20Z

1

In case if you want to proceed both, success and failure result in one callback you should replace calling data with cb(or error as was in your code.

getRequest("http://", function(error, data){
  if(error) throw error
  console.log(data)
});

function getRequest(url, cb, data) {
  request({
      method: 'GET',
      uri: url,
      headers: {
        'Content-Type': 'application/json',
        'dataType': 'json'}
    }, function (error, response, body){
      if(cb) {
          cb(error, JSON.parse(body))
      }
    })
}

Otherwise, you should check if both callbacks provided

function getRequest(url, success, error) {
  request({
      method: 'GET',
      uri: url,
      headers: {
        'Content-Type': 'application/json',
        'dataType': 'json'}
    }, function (error, response, body){
      if(error && failure) {
         failure(error)
      } else if(success) {
         success(JSON.parse(body))
      }
    })
}

In this case, you should provide two callback functions, first for success result and a second one for error which is less common pattern.

answered Sep 5, 2016 at 11:58

G07cha

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3 Comments

tadman Over a year ago

Using a single callback of the form function(error, body) is more consistent here.

G07cha Over a year ago

@tadman, you're absolutely right, I've added a remark about that but I'm not sure if it fits OP needs so just in case provided another option.

tadman Over a year ago

Node.js is pretty adamant about keeping things consistent that way and while I thought it was strange when I started with it, that habit does keep your code a lot more orderly. The wild-west approach from before with dozens of contradictory callback methods is fading into history.

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