WebFund 2013F Lecture 15

Notes

Assignment 3 Tips

• Question 6 : Every time the user score changes, you can update the high score
  • Cheating! It doesn’t have to be constantly updated in the background
  • Or could use long poling
    • Do ajax type call on the client
    • On the server you would wait, set up a callback for when the high score changes
• Question 4:
  • var container = $(‘#container’);
    • returns a jQuery object
  • //for the canvas:
    • c = $(‘canvas’)[0];
  • Anil will post something online about the problem errorsount.play();
  • Need to use jQuery equivalent for the container.offsetLeft etc in function init()

Going through tutorial 9

• In package.json there is a new line:
  • "validator": "*"
    • used for sanitizing user input
    • req.session.player = sanitize(player).escape();
      • sanitize sooner rather than later
      • we only used this in the start function because this is the only user input that was taken
• Want to send something back to the client?
  • You can just use ‘send’ in node
• Complexity has been moved to the client code
• On the browser:
  • If you want privacy, the only way you have it is doing it within functions!
    • In public/javascripts/adventure.js
      • Anonymous function is defined
      • Prevents you from polluting the global file scope
  • In public/javascripts/adventure.js
    • $.getJSON("/getContents", function(room)
      • Get JSON object from server
      • getContents is a function in routes/index.js
      • this will return a page with an enoded JSON object
        • jQuery will happily convert this
  • var exits;
    • doesn’t do anything

	$('.exits').remove();
		    room.roomExits.forEach(function(theExit) {
			$('#exitList').append(
			    '<button type="button" id="' + theExit +
				'" class="btn btn-default exits">'
				+ theExit + '</button>');
			$('#'+theExit).on('click', function() {
			    $.post("/doAction", {action: "move",
						 room: theExit});
			    getRoom();
			});
		    });

• • • Get rid of all of the exits
    • Add button
    • Add even handler
    • When someone clicks on the mouse, it creates another post
    • The value of the exit is coming from the argument to the function
    • Array objects in JavaScript have a standard object called foreach
  • Every webpage defines its own JavaScript scope
    • Script is similar to include in C
  • Implications of scripts
    • You don’t know what code you’re incorporating
    • It changes from minute to minute
    • It runs in the same executions context of your code
    • You have to deal with the DOM – it is global and everyone potentially has access to it
      • What’s to say that code isn’t changing your code
      • There are some things you can do, but it’s not easy