Thanks, Alexandre, it's kind of you to say that. About this code...
> datascape.myInterval = setInterval(window.datascape.move,400); Let's break it down a little. It's exactly the same as doing: var callback = window.datascape.move; datascape.myInterval = setInterval( callback, 400 ); As you can see from this code, JavaScript doesn't "remember" that the callback function was a property of the datascape object. When you get a reference to the function, that's all you get, a reference to the function itself, without any information about what object the function may have been a method of. So when setInterval calls the function later, it just calls it as a plain old function, and "this" is the global/window object. Doesn't ActionScript work the same way? It may have a different global object, but I thought most of the JavaScript semantics were similar except for the ActionScript extensions. I haven't worked with ActionScript so I don't know. -Mike > From: Alexandre Plennevaux > > Michael, did you know that i 'm becoming a big fan of your > explanations? > > if i follow your explanation correctly, this should have > worked, isn't it ? > > datascape.myInterval = setInterval(window.datascape.move,400); > > Yet it didn't. I guess i 'm kind of assimilating the > javascript window object to actionscript's _root object, and > that assumption is probably plain wrong :) > > > On Fri, Jan 2, 2009 at 11:49 PM, Michael Geary <m...@mg.to> wrote: > > > > Hi Alexandre, > > > > Don't go adopting a coding practice just because of a > single mailing > > list message. :-) > > > > There's nothing wrong with quoting property names in an object > > literal, but the majority of experienced JavaScript > programmers do not > > quote them except when necessary. As an example, browse > through the jQuery source code: > > > > http://ajax.googleapis.com/ajax/libs/jquery/1.2.6/jquery.js > > > > Most of the property names in the code are not quoted, except for > > those few that are invalid identifiers or reserved words. > > > > Regarding setTimeout and setInterval, a minor nitpick on > terminology: > > "setTimeout and setInterval scope the called function to > the window object". > > Actually, the *scope* of the called function is determined by its > > position in the source code. JavaScript uses lexical > scoping, where a > > nested function can directly refer to variables declared in outer > > functions or in the global scope. That's why your > setInterval callback > > is able to use your thisObj variable, because the > interpreter follows > > the scope chain from the inner function up to the outer > function and finds the variable there. > > > > What you're talking about is the value of "this" in the setInterval > > callback. setInterval and setTimeout call your callback > function as a > > method of the global object (which is the window object in > a browser). > > Or another way to put it is that they don't call the function as a > > method of any object at all, and by default "this" is set > to the global object. > > > > In any case, terminology nitpicks aside, your code is the > right way to > > solve the problem! :-) > > > > -Mike > > > >> From: Alexandre Plennevaux > >> > >> hi donb, according to a lengthy discussion we had on this > mailinglist > >> yesterday the quotes are good practice. see: > >> http://groups.google.com/group/jquery-en/msg/821f4eb134c51d3d > >> (is is just one message on a 31-long thread, if u have time ,read > >> the whole thread it is interesting ) > >> > >> As for this issue after extensive googling i found out that > >> setTimeout and setInterval scope the called function to the window > >> object, not the object the setinterval is called in. > >> > >> Therefore here is how to do it: > >> > >> var datascape = { > >> 'mouseX': 0, > >> 'myInterval': 0, > >> 'create': function(){ > >> > >> var thisObj = this; //<-- store this object instance in > a variable > >> > >> $('#datascape').bind('mousemove', function(e) > >> { > >> this.mouseX = e.pageX; > >> }).bind("mouseover", function() > >> { > >> datascape.myInterval = setInterval(function() { > >> thisObj.move(); }, 1000); // <-- use the vairable referencing the > >> instance > >> > >> }).bind("mouseout", function() > >> { > >> clearInterval(datascape.myInterval); > >> }); > >> }, > >> > >> 'move': function(){ > >> $.log('datascape.move : mouseX = ' + this.mouseX); > >> } > >> } > >> > >> On Thu, Jan 1, 2009 at 3:46 PM, donb > >> <falconwatc...@comcast.net> wrote: > >> > > >> > You should change 'move' to move (remove apostrophes). > >> > > >> > > >> > On Jan 1, 9:01 am, "Alexandre Plennevaux" <aplennev...@gmail.com> > >> > wrote: > >> >> Hello mates, > >> >> > >> >> i have an object datascape which among other things, contains a > >> >> property storing the mouse position, and a function > that uses that > >> >> property. Inside another method i > >> >> > >> >> var datascape = { > >> >> 'mouseX': 0, > >> >> 'myInterval': 0, > >> >> 'create': function(){ > >> >> $('#datascape').bind('mousemove', function(e) > >> >> { > >> >> this.mouseX = e.pageX; > >> >> }).bind("mouseover", function() > >> >> { > >> >> this.myInterval = setInterval(this.move, 200); > >> >> > >> >> }).bind("mouseout", function() > >> >> { > >> >> clearInterval(this.myInterval); > >> >> }); > >> >> }, > >> >> > >> >> 'move': function(){ > >> >> $.log('datascape.move : mouseX = ' + this.mouseX); > >> >> } > >> >> > >> >> } > >> >> > >> >> Yet the script does not work: > >> >> firebug console points at the setInterval call, saying: > >> >> > >> >> useless setInterval call (missing quotes around > >> >> argument?)http://localhost/prototype/_js/frontend/proto.03.js > >> >> Line 172 > >> >> > >> >> can someone help me / explain what i'm doing wrong ? > >> >> > >> >> Thank you, > >> >> > >> >> Alexandre > >> >> > >> >> PS: to all jquerians: happy 2009 !! > >> > > > > >
