How to use .type into evaluate in Nightmare

I've something like this in my code...

.type("#fieldID", 10)
.evaluate(function () {
     var a = 5;
     var b = 6;
     if(b<=5){var number = a + b; }
     else {var number = a + 5; }
})

I need to put the " .type("#fieldID", 10) " inside .evaluate like this...

.evaluate(function () {
    var a = 5;
    var b = 6;
    if(b<=5){var number = a + b; }
    else {var number = a + 5; }
    .type("#fieldID", number)
})

can anyone please tell me how to do this...?

Thanks.. :)

via Kunkuma Geeth Prasanna