Calling built-in methods on host objects

[RobG]

The following works provided obj is a native object and sufficiently
array-like:

var obj = {'0':'0','1':'1','2':'2', length: 3};
var a = Array.prototype.slice.call(obj);

However, if obj is a host object that is array-like (e.g. a NodeList),
it works in some browsers and not in others - it fails in IE 6 with a
NodeList.

Can someone tell me if it works in some later version of IE, and if
there are other browsers in which it also fails?

 

[Martin Honnen]

The following works provided obj is a native object and sufficiently
array-like:

var obj = {'0':'0','1':'1','2':'2', length: 3};
var a = Array.prototype.slice.call(obj);

However, if obj is a host object that is array-like (e.g. a NodeList),
it works in some browsers and not in others - it fails in IE 6 with a
NodeList.

Can someone tell me if it works in some later version of IE, and if
there are other browsers in which it also fails?

var elements1 = document.getElementsByTagName('*');
var elements2 = Array.prototype.slice.call(elements1, 2);
elements1.length + '\r\n' + elements2.length

throws an error (German message "JScript-Objekt erwartet", my
translation "JScript object expected") in IE 8.

IE 9 has a new JScript engine specifically written to work inside IE so
it might work there, but I haven't yet tested.

 

[Martin Honnen]

IE 9 has a new JScript engine specifically written to work inside IE so
it might work there, but I haven't yet tested.

Tested

var elements1 = document.getElementsByTagName('*');
var elements2 = Array.prototype.slice.call(elements1, 2);
elements1.length + '\r\n' + elements2.length

in IE 9 release candidate, it works flawlessly without throwing any
errors. At least in standards mode, in quirks mode it throws the
following error "Message: Array.prototype.slice: 'this' is not a
JavaScript object".

 

[RobG]

Tested

var elements1 = document.getElementsByTagName('*');
var elements2 = Array.prototype.slice.call(elements1, 2);
elements1.length + '\r\n' + elements2.length

in IE 9 release candidate, it works flawlessly without throwing any
errors. At least in standards mode, in quirks mode it throws the
following error "Message: Array.prototype.slice: 'this' is not a
JavaScript object".

Thanks, I guess that means IE 9 in quirks mode and IE < 9 will all
throw an error. No doubt the mobile version will give similar results
(if the IE 9 script engine is available there).

 

[David Mark]

Thanks, I guess that means IE 9 in quirks mode and IE < 9 will all
throw an error. No doubt the mobile version will give similar results
(if the IE 9 script engine is available there).

See the QSA add-on for My Library for a basic cross-browser solution
(converts host objects to arrays). It's the only place I used that as
I didn't want try-catch in the core back then (though not really
concerned now).