UserScript根據按鍵執行操作？

Question

我與語法這個用戶腳本我想寫，應基本遵循這樣的邏輯掙扎：

IF (LeftArrowKeyIsPressed) THEN doSomething; 
ELSE IF (RightArrowKeyIsPressed) THEN doSomethingElse; 
ELSE IF (any other key pressed) THEN doNothing;

有人可以幫助我的代碼語法結構化檢查的按鍵？假設正在使用onkeydown事件。

Answer 1

使用addEventListener添加一個事件監聽器，可能是窗口。然後關掉Event.which的價值做你想做的。

這是代碼。 See it in action at jsFiddle.：

/*--- Get or set the codes for the arrow keys. 
    Firefox gives us nice constants, Chrome does not. 
*/ 
KeyEvent  = (typeof KeyEvent === "object") ? KeyEvent : []; 
const LEFT_KEY = KeyEvent.DOM_VK_LEFT || 37; 
const RIGHT_KEY = KeyEvent.DOM_VK_RIGHT || 39; 

window.addEventListener ("keydown", keyboardHandler, false); 

function keyboardHandler (zEvent) { 
    var bBlockDefaultAction = false; 

    //--- Assume we want only the plain keys, not the modified versions. 
    if (zEvent.altKey || zEvent.ctrlKey || zEvent.shiftKey) { 
     //-- Do nothing (most user-friendly option, in most cases). 
    } 
    else { 
     if (zEvent.which == LEFT_KEY) { 
      //DO LEFT KEY ACTION HERE. 
      bBlockDefaultAction = true; 
     } 
     else if (zEvent.which == RIGHT_KEY) { 
      //DO RIGHT KEY ACTION HERE. 
      bBlockDefaultAction = true; 
     } 
    } 

    if (bBlockDefaultAction) { 
     zEvent.preventDefault(); 
     zEvent.stopPropagation(); 
    } 
} 

---

此代碼的工作就userscripts適用的瀏覽器（IE沒有）。 jQuery的版本是，除了改變addEventListener線相同的：

$(window).keydown (keyboardHandler);