How do I use javascript to click OK on a standard alert for iphone UI

HI, I'm pretty new to scripting but I'm automating test scripts for the iphone. I'm expecting a standard alert named "Unable to Log In" when I click a login button. However, I am unable to automate the clicking of the 'OK' button on the alert.

I am new 开发者_JS百科to this so please forgive my ignorance if this sounds like a stupid question.

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The UIAApplication should return the alert through its alert property.