event.keycode vs event.which

问题

I fell foul of a Firefox keydown behavior in that pressing the enter key (indeed any key) without having focus on a specific field will NOT trigger a keydown event it will only trigger a keypress event.

This could be very confusing as the keydown and keyup event use JavaScript key codes whereas keypress uses ASCII codes. Fortunately 13 (enter/return) is common to both.

Is there any known reason why FF using keypress in this circumstance? What is the benefit?

Once this was established IE8 threw up a silly in that it does not permit preventDefault demanding instead returnValue = false the following snippet from another SO post has proved very useful:

event.preventDefault ? event.preventDefault() : event.returnValue = false;

During the search to resolve these issues I have been consistently confused by event.keycode vs event.which. Namely am I doing wrong using a switch statement similar to:

$("#class_Name").bind("keydown", function(event){
    // do not test input if field controls used
    switch(event.which){
       case 13:
       //enter key 
       event.preventDefault ? event.preventDefault() : event.returnValue = false;
       break;
     }

Is the following better, if so why?

$("body").keypress(function(event){
     // stop inadvertant form submission
     if (event.keycode == "13"){
       event.preventDefault ? event.preventDefault() : event.returnValue = false;
     }
});

I would just like to know so that I know which is best to apply.

Many thanks.

回答1:

Some browsers use keyCode and others use which. But with jQuery this is normalized so you don't have to think about that. You can just choose the one you prefer.