关于“函数xy（）{…}”的语法错误？

Question

How can I fix the following javascript error ? This is a handler for an ASP.NET page to disable postbacks when the enter key is pressed:

        <script type="text/javascript">
            function document.onkeydown() {

                if (event.keyCode == 13) {
                    event.returnValue = false;
                    event.cancel = true;
                }
            }
        </script>

Answer 1

Note that document.onkeydown is not a valid function name. You probably wanted to do this:

document.onkeydown = function(ev) {
  if (ev.keyCode == 13) {
  // ...
}

Or better:

document.addEventListener('keydown', function(ev) {
  if (ev.keyCode == 13) {
  // ...
});

Answer 2

To add to maerics answer, to get access to the event, you need it as an argument...

document.addEventListener( 'keydown', function( event ) {
    console.log( event, event.keyCode );
    if (event.keyCode == 13) {
        event.returnValue = false;
        event.cancel = true;
    }
});