NodeJS http.request not returning data even after specifying return on the 'end' event
Basically I am trying to scrap some data from website and perform the DOM extraction, deletion and updation on a callback function binded to the 'end' event of http.request .
I have returned the data from the 'end' event callback too but it is not receiving in my route callback function. I get undefined there.
Below is the code block:
var scraper = {
extractEmail: function (directoryName) {
var result = getDirectory(directoryName);
if (result !== 404) {
var protocol = result.https ? https : http;
protocol.request({
host: 'somevalue.net',
method: "GET"
}, function (res) {
var data = '';
res.on('data', function (chunk) {
data += chunk;
});
res.on('end', function () {
return data;
});
})
.on('error', function (err) {
return err;
})
.end();
//return data;
}
else {
//return "Failed";
}
}
};
And here is the Routes.js function:
app.get('/:directory', function (req, res) {
var n = scraper.extractEmail(req.params.directory);
console.log(n);
res.send(n);
});
In here also I don't get the value of n .
Is your 'var scraper' also in the route.js file? I guess it's not and you are unable to access that other js file, for doing so use module.exports.
eg.
// module.js
var name = "foobar";
// export it
exports.name = name;
Then, in route.js...
> //route.js
> // get a reference to your required module
> var myModule = require('./module');
> //correct path to folder where your above file is
> // name is a member of myModule due to the export above
> var name = myModule.name;
You cannot return a value from an asynchronous callback. Well, you can, but it most likely will get ignored and most certainly won't do what you want.
You cannot even return a promise in that place. You can only resolve a promise where you now use the return statements. You need to return a promise from the main function and then resolve or reject the promise in your event handlers where you use returns now.
For more info see those answers:
The simplest modification that will make this work is to pass a callback function to extractEmail to receive the data once it's ready.
var scraper = {
extractEmail: function (directoryName, cb) {
var result = getDirectory(directoryName);
if (result !== 404) {
var protocol = result.https ? https : http;
protocol.request({
host: 'somevalue.net',
method: "GET"
}, function (res) {
var data = '';
res.on('data', function (chunk) {
data += chunk;
});
res.on('end', function () {
cb(null, data);
});
})
.on('error', function (err) {
cb(err);
})
.end();
}
else {
cb(new Error('Failed'));
}
}
};
And use it like this:
app.get('/:directory', function (req, res) {
scraper.extractEmail(req.params.directory, function(err, n) {
if (err) return console.error(err);
console.log(n);
res.send(n);
});
});