nice example, now i think i get it. Indeed actionscript (v2 at least) is based on ecmascript, much like javascript if i'm not mistaken. I came to web design/dev from actionscript one and gradually made my way to jquery. Anyway, actionscript keeps you away from the internal cooking by using a metaphor, "timeline": basically you work with objects and organise them on a main timeline, "_root" (or "_level0"). Each object has its own timeline, can be put inside another object, so you would address it as _root.myStepMother.face.hairyChin;
I wrongly assumed javascript would allow me to do it for setInterval(). hehe, how boring would be the world without all these little variations, now wouldn't it :) ? That's pretty much the problem with using metaphors: it's nice to get you fast into a certain task, but you have to actually break it up to be able to master the technology behind. Thank you Mike and Peter for your excellent help ! On Sat, Jan 3, 2009 at 2:44 AM, Michael Geary <m...@mg.to> wrote: > > 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 !! >> >> >> > >> > >> > >
