a proposed grader.js

grader.js

@@ -0,0 +1,73 @@
+#!/usr/bin/env node
+/*
+   Automatically grade files for the presence of specified HTML tags/attributes.
+   Uses commander.js and cheerio. Teaches command line application development
+   and basic DOM parsing.
+
+   References:
+
+   + cheerio
+   - https://github.com/MatthewMueller/cheerio
+   - http://encosia.com/cheerio-faster-windows-friendly-alternative-jsdom/
+   - http://maxogden.com/scraping-with-node.html
+
+   + commander.js
+   - https://github.com/visionmedia/commander.js
+   - http://tjholowaychuk.com/post/9103188408/commander-js-nodejs-command-line-interfaces-made-easy
+
+   + JSON
+   - http://en.wikipedia.org/wiki/JSON
+   - https://developer.mozilla.org/en-US/docs/JSON
+   - https://developer.mozilla.org/en-US/docs/JSON#JSON_in_Firefox_2
+ */
+
+var fs = require('fs');
+var program = require('commander');
+var cheerio = require('cheerio');
+
+var HTMLFILE_DEFAULT = "index.html";
+var CHECKSFILE_DEFAULT = "checks.json";
+
+var assertFileExists = function(infile) {
+  // error checking, with emergency exit
+  var instr = infile.toString();
+  if(!fs.existsSync(instr)) {
+    console.log("%s does not exist. Exiting.", instr);
+    process.exit(1); // http://nodejs.org/api/process.html#process_process_exit_code
+  }
+  return instr;
+};
+
+var checkData = function(data, checks) {
+  // does the heavy lifting:
+  // - data is a Buffer from file or url
+  // - checks is JSON parsed and sorted
+  $ = cheerio.load(data);
+  var out = {};
+  for(var ii in checks) {
+    var present = $(checks[ii]).length > 0;
+    out[checks[ii]] = present;
+  }
+  console.log(JSON.stringify(out, null, 4));
+};
+
+if(require.main == module) {
+
+  program
+    .option('-f, --file <html_file>', 'Path to index.html')
+    .option('-c, --checks <check_file>', 'Path to checks.json')
+    .parse(process.argv);
+
+  // if the checks file, or default, exists, get checks
+  var checksfilename = program.checks || CHECKSFILE_DEFAULT;
+  var checksfile = assertFileExists(checksfilename);
+  var checks = JSON.parse(fs.readFileSync(checksfile)).sort();
+
+  // if the file parameter, or default, exists, checkData
+  var datafilename = program.file || HTMLFILE_DEFAULT;
+  var datafile = assertFileExists(datafilename);
+  checkData(fs.readFileSync(datafile), checks);
+
+} else {
+  console.log("This module really only runs well as main.");
+}