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JavaScript onkeydown Events
The onkeydown event is triggered when a user presses a keyboard key. Unlike the onkeypress event, the onkeydown event responds to any key-pressed processing (including function keys), and the onkeypress event responds only to the processing of the character key as it is pressed.
Tips
The Internet Explorer/chrome Browser uses Event.keycode to retrieve the characters that are pressed, while browsers such as Netscape/firefox/opera use Event.which.
OnKeyDown gets the key that the user pressed
Here is an example of using the onkeydown event to get the user to press the keyboard key information:
Copy CodeThe code is as follows:function Nonumbers (e)
{
var keynum;
var Keychar;
Keynum = window.event? E.keycode:e.which;
Keychar = String.fromCharCode (keynum);
Alert (keynum+ ': ' +keychar);
}
</script>
<input type= "text" onkeydown= "return Nonumbers (event)"/>
</body>
As shown in the example above, Event.keycode/event.which is given a numeric value (Unicode encoding) corresponding to a key, and the common key values correspond to the following:
| Numeric value | actual key value |
|---|---|
| 48 to 57 | 0 to 9 |
| 65 to 90 | A to Z (A to Z) |
| 112 to 135 | F1 to F24 |
| 8 | BackSpace (BACKSPACE) |
| 9 | Tab |
| 13 | Enter (enter) |
| 20 | Caps_lock (Caps Lock) |
| 32 | Space (space bar) |
| 37 | Left (Rightwards Arrow) |
| 38 | Up (UP ARROW) |
| 39 | Right (Rightwards Arrow) |
| 40 | Down (down arrow) |
In WEB applications, it is often possible to see the Event.keycode/event.which of the onkeydown event to get some of the user's keyboard operations to run some examples of use. If you press the CAPS LOCK key (20) when the user logs in, the CAPS Lock is indicated, and when the user presses the left and right arrows, the flip page is triggered.
After obtaining the Unicode encoded value, if you need to get the actual corresponding key value, you can get it through the fromCharCode method (String.fromCharCode ()) of the Srting object. Note that the characters obtained are always uppercase, and for some other function keys, the resulting characters may not be easy to read.
PS: Here we recommend an online query tool for JS event, and summarize the usual event types and functions of JS:
JavaScript event and Function description Daquan:
Http://tools.jb51.net/table/javascript_event
JavaScript onkeydown Event Starter instance (keyboard key pressed)
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