I am calling a function like below. Here I am also passing callback function that should be called only after a particular form submit not before that.
<div onClick="myNamespace.openDialog(par1,par2,myNamespace.callback(myNamespace.cb,'p1','p2'))">OPEN DIALOG</div>
var myNamespace = myNamespace || {};
myNamespace={
return{
cb:function(p1,p2){alert(p1+" cb "+p2);},
callback:function(f){f(arguments[1],arguments[2]);},
openDialog:function(p1,p2,f){
// aboutBizzNs.cb should be called here only after form submit
}
}
}();
The problem is alert(p1+" cb "+p2);
is called just after OPEN DIALOG
is clicked. It should not be like that. It should be called only when I want. What is the problem
The problem is that aboutBizzNs.callback
immediately invokes the function supplied as an argument.
Compare with the following which creates and returns a closure (function) which will invoke the function supplied when it iself is invoked:
callback: function(f){
// The f variable is bound in a closure below, which is returned immediately.
// However, the f function is NOT invoked yet.
// We also copy the arguments of this function invocation and expose
// them via a variable which is also bound in the following closure.
var boundArgs = Array.prototype.slice(arguments, 0);
return function () {
// Now f is invoked when this inner function is evaluated, which
// should be in response to the event.
return f(boundArgs[1], boundArgs[2]);}
}
}
I'd also use apply
, as in the following such than an arbitrary number of "bound" parameters can be used ..
return function () {
return f.apply(this, boundArgs.slice(1));
}
.. but this is a fairly common operation and is already supported by Function.prototype.bind
(which is part of ES5 and shim-able in other browsers). As such, the original ..
myNamespace.callback(myNamespace.cb,'p1','p2')
.. could be written as ..
myNamespace.cb.bind(this,'p1','p2')
.. for the same effect here. A difference is the this
inside the callback ( cb
) function may differ as bind
doesn't allow a "pass through" of this
.
Or, just forget about all these special functions and simply wrap the callback as such ..
function () { myNamespace.cb('p1','p2') }
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