Override referenced functions

[limweizhong]

Hi,

Say I have already executed the following code in a JavaScript interpreter:

var x,o1,o2;
x=function(){ alert(this.z); };
o1={z:"o1",t:"o1t"};
o1.alertfunc=x;
o2={z:"o2",t:"o2t"};
o2.alertfunc=x;
o1.alertfunc(); // alerts "o1"
o2.alertfunc(); // alerts "o2"

How do I change the function referenced by x, o1.alertfunc and o2.alertfunc to

function(){ alert(this.t); }

without doing the reassignments all over again?

I know a workaround would be to set x to call another function which I can then modify when necessary, but thought that there might be a better way.

[gits]

what do you mean exactly with your workaround? the following will always output 'o1':

var x,o1,o2;
x=function(){ alert(this.z); };
o1={z:"o1",t:"o1t"};
o1.alertfunc=x;
o2={z:"o2",t:"o2t"};
o2.alertfunc=x;
o1.alertfunc(); // alerts "o1"
o2.alertfunc(); // alerts "o2"
 
// do you mean that?
x=function(){ alert(this.t); };
o1.alertfunc(); 
 
// --> outputs 'o1' - functions aren't passed by reference
 
// so you would need to reassign the func to o1 like:
o1.alertfunc = x;
o1.alertfunc();
 
// --> now it outputs 'o1t' - which is a quite, hmmm,
// 'ugly' way of doing such things :)
 

so you would have to use a bit OO magic :) like this:

var x,o1,o2;
 
// we use an obj and its prototype to declare a func
function baseObj() {}
 
baseObj.prototype.x = function() {
    alert(this.z);
};
 
o1 = {
    z: "o1",
    t: "o1t"
};
 
// we assign the function and bind the scope 
o1.alertfunc = function() {
    baseObj.prototype.x.apply(this, arguments);
}
 
o1.alertfunc(); // --> outputs 'o1'
 
// we modify our basObj's prototype 
baseObj.prototype.x = function() {
    alert(this.t);
};
 
o1.alertfunc(); // --> now output is: 'o1t'
 

kind regards

[limweizhong]

Yes, I actually meant something like that but didn't realise you would need to use "apply" to make it work. Thanks.

So I assume creating new functions is the only way to pass functions by reference? Wouldn't that be quite inefficient...?

Also, why do you need to use an object? I thought you could just replace "baseObj.prototype.x" with "myFunctionName" and it would also work?

[gits]

by using an object you might use much better code then the shown one - i used the obj above to give you some idea of it. if i had to realise something like your example i would use code like the below:

function baseObj(params) {
    for (var i in params) {
        this[i] = params[i];
    }
}
 
baseObj.prototype.alertfunc = function(p) {
    alert(this[p]);
};
 
var o = new baseObj({z: 'o1', t: 'o1t'});
 
o.alertfunc('z');
o.alertfunc('t');
 

there is only one func and you could easyly extend it etc.

kind regards