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I'm trying to understand how to write code with promises. Check my code plz. This is right?

Node.js + request:

request(url, function (error, response, body) {
    if (!error && response.statusCode == 200) {
        var jsonpData = body;
        var json;
        try {
            json = JSON.parse(jsonpData);
        } catch (e) {
            var startPos = jsonpData.indexOf('({');
            var endPos = jsonpData.indexOf('})');
            var jsonString = jsonpData.substring(startPos+1, endPos+1);
            json = JSON.parse(jsonString);
        }
        callback(null, json);
    } else {
        callback(error);
    }
});

Node.js + bluebird + request:

request.getAsync(url)
   .spread(function(response, body) {return body;})
   .then(JSON.parse)
   .then(function(json){console.log(json)})
   .catch(function(e){console.error(e)});

How to check response status? I should use if from first example or something more interesting?

I'm trying to understand how to write code with promises. Check my code plz. This is right?

Node.js + request:

request(url, function (error, response, body) {
    if (!error && response.statusCode == 200) {
        var jsonpData = body;
        var json;
        try {
            json = JSON.parse(jsonpData);
        } catch (e) {
            var startPos = jsonpData.indexOf('({');
            var endPos = jsonpData.indexOf('})');
            var jsonString = jsonpData.substring(startPos+1, endPos+1);
            json = JSON.parse(jsonString);
        }
        callback(null, json);
    } else {
        callback(error);
    }
});

Node.js + bluebird + request:

request.getAsync(url)
   .spread(function(response, body) {return body;})
   .then(JSON.parse)
   .then(function(json){console.log(json)})
   .catch(function(e){console.error(e)});

How to check response status? I should use if from first example or something more interesting?

• javascript
• node.js
• promise
• bluebird

Share Improve this question Follow edited Jun 28, 2015 at 10:04 Sergey P. asked Jun 28, 2015 at 9:20 Sergey P.Sergey P. 19411 silver badge1212 bronze badges 2

• 2 Where did jsonString e from? – thefourtheye Commented Jun 28, 2015 at 9:23
• @thefourtheye sry, forget part for catch(e) {...} – Sergey P. Commented Jun 28, 2015 at 10:05

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 11

You can simply check if the response.statusCode is not 200 in the spread handler and throw an Error from that, so that the catch handler will take care of it. You can implement it like this

var request = require('bluebird').promisifyAll(require('request'), {multiArgs: true});

request.getAsync(url).spread(function (response, body) {
    if (response.statusCode != 200)
        throw new Error('Unsuccessful attempt. Code: ' + response.statusCode);
    return JSON.parse(body);
}).then(console.log).catch(console.error);

And if you notice, we return the parsed JSON from the spread handler, because JSON.parse is not an async function, so we don't have to do it in a separate then handler.

One way to check the status code:

.spread(function(response, body) {
  if (response.statusCode !== 200) {
    throw new Error('Unexpected status code');
  }
  return body;
})

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