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up vote 1 down vote favorite

I want to override jQuery's hide() function on my object. I want it to call my onHide() function and then call original hide().

How to accomplish this?

The simplest code won't pass parameters I guess:

myobject.oldhide = myobject.hide;
myobject.onHide = function() {
   // something
};
myobject.hide = function() {
   this.onHide();
   this.oldhide();
}

jQuery's hide() accepts up to 3 parameters. Can I just define 3 of them?

myobject.oldhide = myobject.hide;
myobject.onHide = function() {
   // something
};
myobject.hide = function(a,b,c) {
   this.onHide();
   this.oldhide(a,b,c);
}
share|improve this question
up vote 5 down vote accepted

You can use .apply() to call the original:

this.oldhide.apply(this, arguments);

which will call oldhide with whatever argument list was passed to your own function, which need not have any declared parameters:

myobject.oldhide = myobject.hide;

myobject.onHide = function() {
   // something
};

myobject.hide = function() {
   this.onHide();
   this.oldhide.apply(this, arguments);
}
share|improve this answer
    
Doesn't this.oldhide.apply(this, arguments) will do the same as this.oldhide(arguments)? – Dims Feb 1 '12 at 20:23
1  
@Dims, no. With the second, arguments is passed as the first (duration) parameter of jQuery's hide. – Matthew Flaschen Feb 1 '12 at 20:31
    
Ah, got it, thanks! And on general question, there is no other way to call old version of function other than keeping it in temporary variable? – Dims Feb 1 '12 at 20:38
    
@Dims no, the temporary variable is pretty much the only way. – Alnitak Feb 1 '12 at 20:46
up vote 2 down vote

Yes, the ones that are not passed in will just be undefined.

share|improve this answer
    
but the code will require changes if a new version of .hide() that takes four parameters comes along.... – Alnitak Feb 1 '12 at 17:46
    
@Alnitak, only the function definition will change. The callers of the function don't have to change anything. – Matthew Flaschen Feb 1 '12 at 17:51
    
sure, but that's why arguments exists - you don't need to declare parameters a, b, c solely to pass them on verbatim to another function. – Alnitak Feb 1 '12 at 17:52
    
@Alnitak, agreed. The main reason would be if they were also used by the wrapper. – Matthew Flaschen Feb 1 '12 at 20:29
up vote 0 down vote

You could cache the old hide using $.proxy.

    myobject.oldhide = $.proxy(myobject.hide, myobject);
    myobject.onHide = function() {
       // something
    };
    //a, b, and c parameters don't have to be passed
    //but if they are they will be forwarded to the old hide.
    //Using $.proxy will preserve the way the old function takes parameters.
    myobject.hide = function(a, b, c) {
       this.onHide();
       this.oldhide(a, b, c);
    };
share|improve this answer
    
I don't understand, how parameters for hide() will pass to oldhide()? For example, if I write myobject.hide(12); from my point of view 12 will be lost since this.oldhide() does not pass it further. Is it true? – Dims Feb 1 '12 at 20:19
    
@Dims I have edited to include information about parameter passing. – sinemetu1 Feb 1 '12 at 21:11

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