How to Tell if myObj.constructor is Enumerable in IE / JScript?

[dhtmlkitchen]

I think this is not possible...


var fnProto = Function().prototype;
var badAss = { constructor : "Chuck Norris" };

result = [
isConstructorEnumerable( fnProto )
,isConstructorEnumerable( badAss )
];


function isConstructorEnumerable( ocean, pacific ) {
var enumerable = false;
// hmmm.
// enumerable = ocean.propertyIsEnumerable( pacific );

return enumerable;
}

expected result: [ false, true ];

Has to work in IE. It seems the only way to tell would be if there's
something else that IE adds to the object constructed in Steps 9-10 of
section 13.2 Creating Function Objects

http://bclary.com/2004/11/07/#a-13.2.2

Unfortunately, IE doesn't properly check the DontEnum flag, so will
return the wrong result for propertyIsEnumerable.

 

[Richard Cornford]

I think this is not possible...


var fnProto = Function().prototype;

You have assigned a reference to the object that is the prototype
property of a new function object returned by - Function() - to the -
fnProto - variable.

var badAss = { constructor : "Chuck Norris" };

result = [
isConstructorEnumerable( fnProto )

Your - isConstructorEnumerable - has two formal parameters, yet you are
only passing one argument to it.

,isConstructorEnumerable( badAss )
];


function isConstructorEnumerable( ocean, pacific ) {
var enumerable = false;
// hmmm.
// enumerable = ocean.propertyIsEnumerable( pacific );

return enumerable;

This function will always return false, as it contains no code that will
change the value assigned to - enumerable.

}

expected result: [ false, true ];

Given the code posted the expected results should be [false, false], but
you did not say what the actual results were.

Has to work in IE.

<snip>

What makes you think it does not 'work' in IE?

Richard.