WebFund 2016W Lecture 13 - Revision history

Zero: Added link to JSFiddle.

2016-04-11T23:17:42Z

Added link to JSFiddle.

← Older revision		Revision as of 23:17, 11 April 2016
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	</source>		</source>

			https://jsfiddle.net/Manouchehri/jy5793dd/

	===storeLogs.js===		===storeLogs.js===

LeeCroft: /* JavaScript Closures */

2016-03-06T14:08:46Z

JavaScript Closures

← Older revision		Revision as of 14:08, 6 March 2016
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	</pre></code>		</pre></code>

	*This gives different answers because x is different in two two instances of <code>g</code>		*This gives different answers because <code>x</code> is different in two two instances of <code>g()</code>
	*You cannot do things like this with C		*You cannot do things like this with C
	*In examforms we have an app.get for list and we have a function in it that has a callback called <code>findCallback()</code>		*In examforms we have an app.get for list and we have a function in it that has a callback called <code>findCallback()</code>

LeeCroft: /* JavaScript Closures */

2016-03-06T14:08:19Z

JavaScript Closures

← Older revision		Revision as of 14:08, 6 March 2016
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	*JavaScript closures are about nesting functions		*JavaScript closures are about nesting functions
	*For example:		**For example:
	<code><pre>		<code><pre>
	var f = function(x) {		var f = function(x) {
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	</pre></code>		</pre></code>

	*This gives different answers because x is different in two two instances of g		*This gives different answers because x is different in two two instances of <code>g</code>
	*You cannot do things like this with C		*You cannot do things like this with C
	*In examforms we have an app.get for list and we have a function in it that has a callback called <code>findCallback()</code>		*In examforms we have an app.get for list and we have a function in it that has a callback called <code>findCallback()</code>
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	**To have <code>findCallback</code> have access to request and response you just need to create different instances of <code>findCallback</code> that have their own copies of request and response, therefore one version of <code>findCallback</code> will have one request and on another call it will have another request		**To have <code>findCallback</code> have access to request and response you just need to create different instances of <code>findCallback</code> that have their own copies of request and response, therefore one version of <code>findCallback</code> will have one request and on another call it will have another request
	*Closure is a concept you need to understand because it’s very handy		*Closure is a concept you need to understand because it’s very handy


	====Client-Side JavaScript====		====Client-Side JavaScript====

LeeCroft: /* Writing storelogs.js */

2016-03-06T14:06:51Z

Writing storelogs.js

← Older revision		Revision as of 14:06, 6 March 2016
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	*We can use the code from storeloglines.js to start building the storelogs.js script for tutorial 5		*We can use the code from storeloglines.js to start building the storelogs.js script for tutorial 5
	To read in a file specified in the command line, you do <code>var data = fs.readFileSync(process.argv[2], ‘utf-8’);</code>		*To read in a file specified in the command line, you do <code>var data = fs.readFileSync(process.argv[2], ‘utf-8’);</code>
	**You use <code>process.argv[2]</code> because in the terminal your third argument is going to be the file to read		**You use <code>process.argv[2]</code> because in the terminal your third argument is going to be the file to read
	*To split the data into lines, yo do <code>var lines = data.split(‘\n’);</code>		*To split the data into lines, yo do <code>var lines = data.split(‘\n’);</code>
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	**It's the previous assignment from last year’s assignment 5		**It's the previous assignment from last year’s assignment 5
	*Note that when using special characters like [] and () in regular expression, you will need to use a backslash to escape them		*Note that when using special characters like [] and () in regular expression, you will need to use a backslash to escape them


	====JavaScript Closures====		====JavaScript Closures====

LeeCroft at 14:06, 6 March 2016

2016-03-06T14:06:04Z

Show changes

Soma at 21:36, 1 March 2016

2016-03-01T21:36:17Z

← Older revision		Revision as of 21:36, 1 March 2016
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	===storeLogs.js===		===storeLogs.js===

			[http://homeostasis.scs.carleton.ca/~soma/webfund-2016w/code/storeLogs.js downloadable version]

	<source lang="javascript" line>		<source lang="javascript" line>

Soma at 21:34, 1 March 2016

2016-03-01T21:34:28Z

← Older revision		Revision as of 21:34, 1 March 2016
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	Now you could update data in a web page without reloading the page		Now you could update data in a web page without reloading the page
	</pre>		</pre>

			==Code==

			===nested.js===

			<source lang="javascript" line>
			var f = function(x) {
			function g(y) {
			return x + y;
			}

			return g;
			}

			var q = f(7);
			var h = f(12);

			console.log("q(4) = " + q(4));
			console.log("h(4) = " + h(4));
			</source>


			===storeLogs.js===

			<source lang="javascript" line>
			// storeLogs.js
			//
			// node storeLogs.js <logfile>
			//
			//
			// The log messages in the file should be of the format:
			// <month> <day of month> <24-hour time in hh:mm:ss> <host> <service name[pid]>: Actual message
			//

			var mc = require('mongodb').MongoClient;
			var fs = require('fs');

			var data = fs.readFileSync(process.argv[2], 'utf-8');

			var lines = data.split('\n');

			var entries = [];

			var i, j, entry, field;

			for (i=0; i<lines.length; i++) {
			if (lines[i] && lines[i] !== '') {
			field = lines[i].split(' ');
			entry = {};
			j = 0;
			while (j < field.length) {
			if (field[j] === "") {
			field.splice(j, 1);
			} else {
			j++;
			}
			}
			entry.date = field[0] + " " + field[1];
			entry.time = field[2];
			entry.host = field[3];
			entry.service = field[4].slice(0,-1);
			entry.message = field.slice(5).join(' ');
			entries.push(entry);
			}
			}

			// entry.date = process.argv[2] + " " + process.argv[3];
			// entry.time = process.argv[4];
			// entry.host = process.argv[5];
			// entry.service = process.argv[6].slice(0,-1); // drop the trailing colon
			// entry.message = process.argv.slice(7).join(' ');

			var db;

			var reportInserted = function(err, result) {
			if (err) {
			throw err;
			}

			console.log("Inserted the following log record:");
			console.log(result.ops);
			db.close();
			}

			var connectCallback = function(err, returnedDB) {
			if (err) {
			throw err;
			}

			db = returnedDB;

			db.collection('logs').insert(entries, reportInserted);
			}

			mc.connect('mongodb://localhost/log-demo', connectCallback);
			</source>

Soma: Created page with "==Video== The video from the lecture given on March 1, 2016 [http://homeostasis.scs.carleton.ca/~soma/webfund-2016w/lectures/comp2406-2016w-lec13-01Mar2016.mp4 is now availab..."

2016-03-01T21:32:00Z

Created page with "==Video== The video from the lecture given on March 1, 2016 [http://homeostasis.scs.carleton.ca/~soma/webfund-2016w/lectures/comp2406-2016w-lec13-01Mar2016.mp4 is now availab..."

New page

==Video==

The video from the lecture given on March 1, 2016 [http://homeostasis.scs.carleton.ca/~soma/webfund-2016w/lectures/comp2406-2016w-lec13-01Mar2016.mp4 is now available].

==Notes==

===In lecture===
<pre>
Lecture 13
----------

To get help with assignment 4, look at Assignment 5 from Winter 2015.

closures

DOM
- document object model
- set of JavaScript objects for accessing the current page in the browser

client-side JS can access the DOM
(data structures representing the current web page)

server-side JS can access the operating system

client-side JS is *limited* in its access
- because such access is dangerous
- ANYONE can run JavaScript in your browser
- so, JavaScript in the browser is sandboxed

execution sandbox is an environment for running untrusted programs
- sandbox limits access and resources

Client-side JavaScript has no native way to
(well, it used to...)
- access local files
- open network connections
- run multiple threads
- access other windows/programs

Originally JavaScript was so limited it could do no background processing
- could only run when the page was loaded or when the user acted

Microsoft messed it up
- Outlook Web Access
- they built an ActiveX control which implemented XMLHttpRequest()
- but really, it was a way to do GETs and POSTs in the background
- other browsers implemented the API natively

Now you could update data in a web page without reloading the page
</pre>