prototype Event Observer not working

Please check what i am doing here false?

 Event.observe(form['postalcode'], 'blur', function(form) {return  updateCityname(form) }(form)); 

I am getting Javascript error "handle开发者_如何学JAVA is undefined"

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Give this element an ID of "postalCode", it makes it a lot easier.

   $('postalCode').observe('blur', function(e) {
        var element = e.element()        
        var myForm = element.up('form')
        return updateCityname(myForm) 
    });