How to catch error on http.get - javascript

I have some http.get code that looks like this
http.get(url, function (response) {
var data = '';
response.on('data', function (x) {
data += x;
});
response.on('end', function () {
var json = JSON.parse(data);
console.log(json);
});
});
How do I error handling this if an invalid URL/API endpoint is provided?

you can handle http.get errors by check state error example:-
http.get(url, function (response) {
response.on('error', function (err) {
//do some thing , error handling
console.log(err);
});
});
you can validate the url by
validating response code & ping domain or url
1 - validate response code :-
http.get(url, function (response) {
if(response.statusCode !== 200){
//error happens
}
});
2- ping on the giving url using this repo valid-url:-
var validUrl = require('valid-url');
if (!validUrl.isUri('apiUrl')){
//error not valid url
}

Related

Node js sending multiple requests after 20 secs

My node js app is making multiple http request if there is delay in response of say 20 secs. Below is the sample code for the same.
First I make call to the getAPI function from browser. getApi function calls the getAccessToken API, after receiving the accesstoken I am calling the testApi. Now if there is a delay of 20 secs in response from testApi then getAccessToken Api is getting called again. I don't want to use promise. Can anyone point out what I am missing or doing wrong here?
shttp = require('http-https');
exports.getAPI = function(typeObj, request, response, callback) {
var userConf; //contains info such as port, host, url etc
_this.getAccessToken(function(tokenResponse) {
var tokenInfo = JSON.parse(tokenResponse);
var accessToken = JSON.parse(tokenInfo.response);
accessToken = accessToken.access_token;
if(accessToken) {
_this.testApi(userConf,accessToken,function(sjmResponse) {
callback(sjmResponse);
}
} else {
callback(JSON.stringify({"payLoad":null,"reasonCode":"fail","status":null}));
}
});
};
exports.getAccessToken = function(cb) {
var tokenConf; //contains info such as port, host, url etc
var httpReq = shttp.request(tokenConf, function(res) {
res.setEncoding('utf8');
if (res.statusCode == 200) {
var body = "";
res.on('data', function (result) {
body += result;
});
res.on('end', function (){
cb(JSON.stringify({error: '', response: (body)}));
});
} else {
cb(JSON.stringify({error: 'Failed to get user access token '+res.statusCode, response:''}));
}
});
httpReq.on('error', function(e) {
cb(JSON.stringify({error: 'Failed to get user access token'+e, response:''}));
});
httpReq.end();
};
exports.testApi = function(userConf,accessToken,sjmCallback) {
var userConf; //contains info such as port, host, url etc
var httpSubmitReq = shttp.request(userConf, function(res) {
res.setEncoding('utf8');
if (res.statusCode == 200) {
var body = "";
res.on('data', function (result) {
body += result;
});
res.on('end', function () {
sjmCallback(body);
});
} else {
sjmCallback(JSON.stringify({"payLoad":null,"reasonCode":"fail","status":null}));
}
});
httpSubmitReq.on('error', function(e) {
sjmCallback(JSON.stringify({"payLoad":null,"reasonCode":"fail","status":null}));
});
httpSubmitReq.end();
};
app.get('/testApi', function (req, res) {
var typeObj = {};
typeObj.apiType= 'testApi';
try {
getAPI(JSON.stringify(typeObj), req, res, function(response) {
res.end(response);
});
} catch(err) {
res.end(err);
}
});

node.js async callback error on queue.drain

I am trying to use a callback to indicate when all the async workers are complete, but I am getting the dreaded
TypeError: callback is not a function.
I would like to individually process each element in data, and on completion, have queue.drain to send the callback(data) to refresh Data on completion. I have been readying the async documentation, but clearly i am not getting something.
function refreshData(postData, callback) {
var options = {
host: 'www.myhost.com',
port: 443,
path: '/pulldata,
method: 'POST',
headers: {
"Content-Type": "application/json"
}
};
var req = https.request(options, function(res) {
var headers = res.headers
var d = '';
res.setEncoding('utf8');
res.on('data', function (chunk) {
d = d + chunk;
});
res.on('end', function() {
if (res.statusCode == '200') {
data = JSON.parse(d);
queue = async.queue(function (task, cb) {
processData(task,cb);
},1);
//this is were the errors are
queue.drain = function() {
callback(data)
};
for(i=0; i<data.length; i++) {
queue.push(data[i],'');
}
} else {
callback(false)
}
});
});
req.on('error', function(e) {
console.log('problem with request: ' + e.message);
});
// write data to request body
req.write(postData);
req.end();
}
Any assistance would be greatly appreciated!
Edit, added some pseudo code to demonstrate how refreshData is being used:
Node https.createServer(req,res) {
req.on(){
read userData
}
req.end(){
validateUser(userData, function(callbackData) {
if(callbackData==false) {
//bad user or error with request
res.writeHead(404);
res.end('bye');
} else {
//good user and responses
res.writeHead(200);
res.end(callbackData);
}
})
}
}
function validateUser(userData,callback) {
//do some stuff to validate
if(userData is good) {
//call refreshData if user
refreshData(userData,callback)
} else {
callback(false)
}
}
[EDIT] Added a callback
As given in the documentation you pointed to , change this line
queue.push(data[i],'');
to
queue.push(data[i], function(err){
// handle error
});
Try it here async-queue-callback

passing error message from service to controller in angularjs

Controller.js
var vm = this;
vm.admin = {};
vm.add = function () {
API.addAdmin(token, vm.admin)
.then(function (resp) {
vm.hideForm = true;
vm.showButton = true;
Notify.green(resp);
}, function (resp) {
Notify.red(resp);
});
};
API.js
function addAdmin(token, dataObj) {
return Constant.getApiUrl()
.then(function (url) {
$http({
method: 'POST',
url: url + '/client/admin',
headers: {
'Token': token
},
data: dataObj
}).then(handleResp);
function handleResp(resp) {
var responseStatus = (resp.status >= 200 && resp.status < 300) ? 'good' : 'bad';
if (responseStatus === 'good') {
console.log("Success" + resp);
return resp;
} else {
console.log("Failed" + resp);
return resp;
}
}
})
}
If I get a success response in API then i need to connect it to success function in my controller and if i get error message in my API, then i need it to connect it to error function in my controller.How should I evaluate the response status from my API(is either success or error).
I don't want to pass successfn, errorfn from my controller to API(only if there's no alternative).
I need to get the response data from API to controller to show it in Notify message.
Thank You!
In service (assign response values in "originalData"):
angular.module('appname').service('myserviceName', function(yourExistingService){
this.myFunction= function(originalData) {
//for next line to work return promise from your addAdmin method.
var promise = yourExistingService.getResponseFromURL(originalData);
return promise;
}
});
And in your controller :
var promise = myserviceName.myFunction($scope.originalData);
promise.$promise.then(function() {
console.log($scope.originalData);
});
And then you can check you "originalData" and write code according to your need.For more detail you can have a look on this http://andyshora.com/promises-angularjs-explained-as-cartoon.html.

Why is this basic Node.js error handling not working?

Node.js:
var https = require("https");
var request = https.get("google.com/", function(response) {
console.log(response.statusCode);
});
request.on("error", function(error) {
console.log(error.message);
});
If I add https:// to the google domain name then I get the status code 200 as expected. As is, I would expect the error to be caught and an error message similar to "connect ECONNREFUSED" to be printed to the terminal console. Instead it prints the stacktrace to the terminal.
If you look at the source for https.get(), you can see that if the parsing of the URL fails (which it will when you only pass it "google.com/" since that isn't a valid URL), then it throws synchronously:
exports.get = function(options, cb) {
var req = exports.request(options, cb);
req.end();
return req;
};
exports.request = function(options, cb) {
if (typeof options === 'string') {
options = url.parse(options);
if (!options.hostname) {
throw new Error('Unable to determine the domain name');
}
} else {
options = util._extend({}, options);
}
options._defaultAgent = globalAgent;
return http.request(options, cb);
};
So, if you want to catch that particular type of error, you need a try/catch around your call to https.get() like this:
var https = require("https");
try {
var request = https.get("google.com/", function(response) {
console.log(response.statusCode);
}).on("error", function(error) {
console.log(error.message);
});
} catch(e) {
console.log(e);
}

Javascript Node.js overwrite File completely

i have an application which needs a data.json file in order to draw a d3-graph. However i need to update that file on an onClick-Event:
d3.select("#updatebutton").on("click", function(e) {
try{
$.get('https://localhost:4444/data', function(data) {
});
}
catch (e) {
alert('Error: ' + e);
}
});
Above is the update-Button with the jquery-call. In my app.js File I am using it like this:
app.get('/data', function(req, res, next) {
try{
getJSON();
}
catch(e) {
alert('Error');
}
});
The getJSON()-Function is received Data over an https-Request, processes that data and saves it to data.json:
function getJSON() {
var req = https.get(options, function(response) {
// handle the response
var res_data = '';
response.on('data', function(chunk) {
res_data += chunk;
});
response.on('end', function() {
//process data
// save to file
fs.writeFile(filePath, JSON.stringify(finalJson), function(err) {
if (err)
throw err;
});
});
});
}
However if i click on my updateButton repeatedly after seconds, it seems that data.json is not overwritten but the file gets bigger and bigger, means that data is added to the file instead of overwritten.
What am I doing wrong?
Thanks for help.
Since you use app.get as your route, I guess you are using express.
In your routes definition:
var getData = (function() {
var callbacks = [];
function executeCallbacks(err, data) {
for (var i = 0; i < callbacks.length; i++) {
callbacks[i](err, data);
}
callbacks = [];
}
return function(cb) {
callbacks.push(cb);
if( callbacks.length === 1 ) {
var req = https.get(options, function(response) {
// handle the response
var res_data = '';
response.on('data', function(chunk) {
res_data += chunk;
});
response.once('end', function() {
// process data here
// save to file
fs.writeFile(filePath, JSON.stringify(finalJson), function(err) {
if (err) {
// call error handler
return executeCallbacks(err);
}
executeCallbacks(null, body);
});
});
response.once('error', function() {
return executeCallbacks(err);
});
}
req.end();
}
};
})();
app.get('/data', function(req, res, next) {
getData(function(err, data) {
if(err) {
return next(err);
}
return data;
});
});
In your browser js file:
d3.select("#updatebutton").on("click", function(e) {
$.get( 'https://localhost:4444/data', function(data) {
alert( "success" );
var json = JSON.parse(data);
})
.fail(function() {
alert( "error" );
});
});
I see you use try / catch around callback functions. The callback function fires after the original function completes. So don't use Try / Catch around callback function.
Read: https://strongloop.com/strongblog/async-error-handling-expressjs-es7-promises-generators/

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