JS KeyUp, KeyPress and KeyDown events

JS KeyUp, KeyPress and KeyDown events

JS KeyUp, KeyPress and KeyDown events are all about keyboard events

When a button is pressed or released in every modern browser, there can be three client-side events.

1. KeyDown Event
2. KeyPress Event
3. KeyUp Event

The KeyDown event occurs when the keyboard key is pressed, and then the KeyPress event is triggered. the KeyUp event is triggered when the key is released.

Here are some examples of how these three events are used in the page:

<input id= "testkeyevent" name= "testkeyevent" onKeyUp= "KeyUp ()"/>

<input id= "testkeyevent" name= "testkeyevent" onkeypress= "keypress ()"/>

<input id= "testkeyevent" name= "testkeyevent" onkeydown= "KeyDown ()"/>

The corresponding JS function:

function KeyUp () {...}

function KeyPress () {...}

function KeyDown () {...}

Attention:

2. After the KeyDown is triggered, the keyup is not necessarily triggered, and when the KeyDown is pressed, the mouse is dragged and the KeyUp event is not triggered.
4. KeyPress is primarily used to capture numbers ( Note: Symbols including shift+ numbers ), letters ( Note: include capitalization ), keypads, etc. except f1-12, SHIFT, Alt, Ctrl, Insert, Home, PgUp, Delete, End, PgDn, ScrollLock, Pause, NumLock, {Menu key}, {Start key}, and ANSI characters outside the arrow key
6. KeyDown and KeyUp can usually capture keyboards in addition to prscrn all keys (special keys for special keyboards are not discussed here)
8. KeyPress can only capture a single character
10. KeyDown and KeyUp can capture key combinations.
12. KeyPress can capture the case of a single character
14. The keyvalue of KeyDown and KeyUp for a single character capture is a value, that is, the case of a single character cannot be judged.
16. The KeyPress does not differentiate between the numeric characters of the keypad and the main keyboard.
18. KeyDown and KeyUp distinguish the numeric characters of the keypad and the main keyboard.
20. where Prscrn keys KeyPress, KeyDown, and KeyUp are not captured.

22. When using the keyboard, it is common to use a key combination function similar to Ctrl+shift+alt. How do we determine this?

    Through the KeyUp event can be handled (here to explain why not KeyDown, because in the decision KeyDown, CTRL, Shift and ALT belong to hold the state, and then add another key is not accurately capture the key combination, so use KeyDown Can not be accurately judged by the KeyUp event to determine)

    Here is a simple list of CTRL + other key combination judgment code:

    
    private void Form3_keyup (object sender, KeyEventArgs e)
    {
    if (E.control)
    {
    MessageBox.Show ("keyup:ctrl+" + e.keyvalue.tostring ());
    }
    }
24. Capturing PRSCRN Key Events

    The PRSCRN key event can be determined by means of a hook, and the hook can get any keyboard event.

Here are some of the keys on the keyboard that correspond to code: The following are some of the keys on the keyboard that correspond to code:

Keyboard keys corresponding to the digital

Backspace	8
tab	9
Enter	13
Shift	16
Ctrl	17
Alt	18
Pause/break	19
Caps LOCK	20
Escape	27
Page UP	33
Space	32
Page Down	34
End	35
Home	36
Arrow Left	37
Arrow up	38
Arrow Right	39
Arrow Down	40
Insert	45
Delete	46
0	48
1	49
2	50
3	51
4	52
5	53
6	54
7	55
8	56
9	57
A	65
B	66
C	67
D	68
E	69
F	70
G	71
H	72
I	73
J	74
K	75
L	76
M	77
N	78
O	79
P	80
Q	81
R	82
S	83
T	84
U	85
V	86
W	87
X	88
Y	89
Z	90
Left window key	91
Right window key	92
Select key	93
Numpad 0	96
Numpad 1	97
Numpad 2	98
Numpad 3	99
Numpad 4	100
Numpad 5	101
Numpad 6	102
Numpad 7	103
Numpad 8	104
Numpad 9	105
Multiply	106
Add	107
Subtract	109
decimal point	110
Divide	111
F1	112
F2	113
F3	114
F4	115
F5	116
F6	117
F7	118
F8	119
F9	120
F10	121
F1

JS KeyUp, KeyPress and KeyDown events