Dropdown item price with java script

my issue is that , i have 1 dropdown name Items with 3 items (fruits) i want when someone pick any friut in dropdown the price auto come in price section, i do this java script in price section it's not showing any error but not showing the price too , i have tried many times but stuck in this problem pls guide me where im doing mistake 

var Item = this.getfeild("Items").value;
switch(Item) {

case "Apple":
event.value = "100";
break;

case "Banana":
event.value = "150";
break;

case "Graps":
event.value = "200";
break;

case "Orange":
event.value = "250";
break;

}