onkeyup event

The onkeyup event activates when a keyboard key is released on an element. The event can be specified as a JavaScript expression or the name of a JavaScript function.

If an expression is used, the JavaScript keyword this refers to the element on which the key was released.

If the name of a function is used, the function will receive 2 parameters when called:

The browser event object; this object can be used to retrieve the JavaScript key code for the key released using the keyCode property
A reference to the element on which the key was released

Example:

The following code uses AJAX to retrieve a customer's name as the customer number is being typed into an input box.

onkeyup: getCustomerName

// This function will be called on every key stroke
// When a valid customer number is typed, the customer name will appear on the screen
function getCustomerName(event, element) {
  var customerNumber = element.value;
  ajaxJSON({
    url: "/cgi/GETCUST.pgm",
    params: {
      "CSNUMBER": customerNumber
    },
    method: "post",
    async: true,
    handler: function(response) {
      changeElementValue("CSNAME", response.CSNAME);
    }
  };
}