All of this code is in a file called juggling_async.js. It is exercise 9 of node school.
This code is broken (I wrote it):
var http = require('http');
var bl = require('bl');
var result = [];
var count = 0;
for(var i=0;i<3;i++) {
http.get(process.argv[2 + i], function(res){
res.pipe(bl(function(err,data){
if(err) return console.log(err.message);
result[i] = data.toString();
count++;
if(count == 3) {
for(var j=0;j<result.length;j++) {
console.log(result[j]);
}
}
}));
});
}
It logs out:
"undefined"
"undefined"
"undefined"
"[this is a string of text]"
This code solves the problem:
var http = require('http')
var bl = require('bl')
var results = []
var count = 0
function printResults () {
for (var i = 0; i < 3; i++)
console.log(results[i])
}
function httpGet (index) {
http.get(process.argv[2 + index], function (response) {
response.pipe(bl(function (err, data) {
if (err)
return console.error(err)
results[index] = data.toString()
count++
if (count == 3) // yay! we are the last one!
printResults()
}))
})
}
for (var i = 0; i < 3; i++)
httpGet(i)
In my mind, my broken code should work. I start looping through i, i starts at 0, I make an http.get request using the http library and the http.get takes a callback where res is the response of the http.get request. function(res) is the callback which doesn't run until the get request returns right? At that point, i is still 0 and so I set data.toString() to result[0] right? The first element of the result array then should contain something right and not be undefined?
Obviously, my mind and code are broken. Where am I going about this incorrectly?
BTW:, I read the related posts on closures and I still don't understand why my code is broken or where it's failing.
