key-updown.js

这是《JavaScript学习源代码》一书的源代码

// specify KEYDOWN and KEYUP event-handlers
window.document.onkeydown = isdown; 
window.document.onkeyup = isup;

// a function to react to KEYDOWN events
function isdown()
{
  window.document.getElementById("bulb").src="on.gif";
 
  document.getElementById("txt").value = "Key is Down";  
}           

// a function to react to KEYUP events
function isup() 
{                  
  window.document.getElementById("bulb").src="off.gif";
 
  document.getElementById("txt").value = "Key is Up";     
} 

/* the second statement in each function deliberately omits the optional 搘indow.