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JavaScript onkeydown event entry instance (a key on the keyboard is pressed), javascript button
JavaScript onkeydown event
An onkeydown event is triggered when you press the next keyboard button. Unlike the onkeypress event, the onkeydown event responds to the processing of any key press (including the function key), and The onkeypress event only responds to the processing after the character key is pressed.
Prompt
Internet Explorer/Chrome uses event. keyCode to retrieve the characters that have been pressed, whereas Netscape/Firefox/Opera and other browsers use event. which.
Onkeydown gets the key pressed by the user
The following is an example of using the onkeydown event to obtain the user's press key information:
Copy codeThe Code is as follows:
<Html>
<Body>
<Script type = "text/javascript">
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>
</Html>
As shown in the preceding example, event. keyCode/event. which obtains the numeric value (Unicode encoding) corresponding to a key. The common key value corresponds to the following:
| Numeric Value | Actual key value |
|---|---|
| 48 to 57 | 0 to 9 |
| 65 to 90 | A to z (A to Z) |
| From 112 to 135 | F1 to F24 |
| 8 | BackSpace) |
| 9 | Tab |
| 13 | Enter (Press Enter) |
| 20 | Caps_Lock (Capital lock) |
| 32 | Space (Space key) |
| 37 | Left (Left arrow) |
| 38 | Up (Up arrow) |
| 39 | Right (Right arrow) |
| 40 | Down (Down arrow) |
In Web applications, you can often see that you can use the event. keyCode/event. which of the onkeydown event to obtain some of your keyboard operations and run some examples. For example, when a user logs on, if the capital Lock key (20) is pressed, the system prompts the capital lock; when there is a page flip, if the user presses the left and right arrows to trigger up and down pages.
After obtaining the Unicode encoding value, you can obtain the actual key value through the fromCharCode method (String. fromCharCode () of the Srting object. Note that uppercase characters are always obtained, while some other function buttons may not be easy to read.
Status determination is performed before the binding event is executed. If this event has been executed once, it will not be executed until the keyup status is switched. If you press it again, it will take effect again.
In ACCESS, onkeypress is an event that occurs when the keyboard on the form is pressed, while onkeydown is an event that occurs when the keyboard on the form is pressed.
To understand the differences between the two operations, you must first understand the key actions, which are generally divided into two: one is press, the English is Keydown, the second is to open the key, called Keyup, and the two actions are called Keypress together
Onkeypress is an event triggered when a key is pressed and popped up.
Onkeydown event refers to an event that can be triggered by pressing a key and does not have to wait for a bounce.
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