Toying with node.js
A commenter rightly complained that despite my claims of “playing around” with node.js, all I could come up was with the example in the man page. I replied saying that I did intend to post something that I wrote from scratch, and as promised, here is my first toy node.js program:
var sys = require('sys');
var http = require('http');
var url = require('url');
var path = require('path');
function search() {
stdin = process.openStdin();
stdin.setEncoding('utf8');
stdin.on('data', function(term) {
term = term.substring(0, term.length - 1);
var google = http.createClient(80, 'ajax.googleapis.com');
var search_url = "/ajax/services/search/web?v=1.0&q=" + term;
var request = google.request('GET', search_url, {
'host': 'ajax.googleapis.com',
'Referer': 'http://floatingsun.net',
'User-Agent': 'NodeJS HTTP client',
'Accept': '*/*'});
request.on('response', function(response) {
response.setEncoding('utf8');
var body = ""
response.on('data', function(chunk) {
body += chunk;
});
response.on('end', function() {
var searchResults = JSON.parse(body);
var results = searchResults["responseData"]["results"];
for (var i = 0; i < results.length; i++) {
console.log(results[i]["url"]);
}
});
});
request.end();
});
}
search();
This program (also available as a gist) reads in search terms on standard input, and does a Google search on those terms, printing the URLs of the search results.
I was quite surprised (and a bit embarrassed) at how long it took me to get this simple program working. For instance, it took me the better part of an hour to realize that when I read something from stdin, it includes the trailing newline (as the user hits ‘Enter’). Earlier, I was using the input as-is for the search term, and that was leading to a 404 error, because the resulting URL was malformed.
Debugging was also harder, as expected. Syntax errors are easily caught by V8, but everything else is still obscure. I’m sure some of the difficulty is because of my lack of expertise with Javascript. But at one point, I got this error:
events:12
throw arguments[1];
^
Error: Parse Error
at Client.ondata (http:881:22)
at IOWatcher.callback (net:517:29)
at node.js:270:9
I still haven’t figured out exactly where that error was coming from. Nonetheless, it was an interesting exercise. I’m looking forward to writing some non-trivial code with node.js now.
