Question

This was an example from our prof and my HTML is rusty so I’m not sure exactly what is going on.
For the form input:

<input type="text" name="widgets" id="widgets" size="2" value="0" onchange="calc();" onkeypress="return isNumberInput(this, event);" />

For the Javascript:

function isNumberInput(field, event)
{
var key, keyChar;
if (window.event)
key = window.event.keyCode;
else if (event)
key = event.which;
else
return true;
// Check for special characters like backspace
if (key == null || key == 0 || key == 8 || key == 13 || key == 27)
return true;
// Check to see if it.s a number
keyChar = String.fromCharCode(key);
if (/\d/.test(keyChar))
{
window.status = "";
return true;
}
else
{
window.status = "Field accepts numbers only.";
return false;
}

Can someone explain what is going on? I’m not too familiar with window.event, event.which, wondow.event.keyCode, etc. I don’t really understand the logic. TIA!

Answer 1

var key, keyChar; // declare variable to be used
if (window.event) // window.event Microsoft uses window.event. Does it exist? If so continue
    key = window.event.keyCode; // Microsoft uses window.event.keyCode to get the key the was pressed
else if (event) // other modern browsers will create an event object for you to use
    key = event.which; // event.which is the key that was pressed
else // else we can't get to the key maybe this is a full text browser? Anyways, no good exit function
    return true;