Вот простое решение:
//declare string to write,
//then split it at each letter,
//then get the total number of letters,
//declare a starting index of zero,
//then set a timer for an interval
var string = 'hello there',
letters = string.split(''),
total = letters.length,
index = 0,
$ele = $('input'),//this should be changed to target the form input you want to type into
timer = setInterval(function () {
//check if there are any more letters
if (index < total) {
//if there are more letters then add the next letter to the input
$ele.val(function () {
return $ele.val() + letters[(index++)];
});
//if there are no more letters then clear the interval so it stops running
} else {
clearInterval(timer);
}
}, 500);
Вот демоверсия: http://jsfiddle.net/pCVE6/