Javascript method that executes a test periodically until true, then triggers an action with the result of the test.

when.js

var when = function( test, execute, delay ) {
    delay = delay || 200;
    var x = test();
    if ( x ) {
        execute( x );
    } else {
        setTimeout( function() {
            when( test, execute, delay );
        }, delay );
    }
}

when( 
    function() { return confirm('Stop?');}, 
    function( x ) { alert('finally: ' + x); }
);