I've always found this bit of code useful:
var rescope = function(scope, method){
if(!method){ method = scope; scope = null; }
if(typeof method == "string"){
scope = scope || window;
if(!scope[method]){ throw(['method not found']); }
return function(){ return scope[method].apply(scope, arguments
|| []); };
}
return !scope ? method : function(){ return method.apply(scope,
arguments || []); };
}
An example:
var myObj = {
interval: 1000,
count: 0,
start: function(){
if(this.timer){ return; }
this.timer = setInterval(rescope(this, "update"),
this.interval);
},
stop: function(){
clearInterval(this.timer);
delete this.timer;
},
update: function(){
console.log(++this.count);
}
};
myObj.start();
Regards,
Peter Higgins
On Fri, Jan 2, 2009 at 5:49 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 !!
>>
>
>
