If the function is expected as a property of some object (including
`window`), then I'd probably do this:

    if (typeof obj.functionName == 'function')

So for instance:

    if (typeof window.globalEval == 'function')

If you need to check whether a function is defined in the current
scope and not on a property (so, on the current variable object or one
of the others in the scope chain), I'd probably be a bit more

    var defined = false;
    try {
        defined = typeof functionName == 'function';
    catch (e) {

Prototype also adds a function to `Object` that does the check:

    if (Object.isFunction(window.globalEval))

...which is just a shorthand way of doing the typeof.

T.J. Crowder
Independent Software Consultant
tj / crowder software / com

On Feb 4, 3:14 pm, RK <rajkishore.puj...@gmail.com> wrote:
> How would you check if a function is defined using prototype
> Thanks,
> RK.

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