javascript - window.event fails when called from setTimeout -

i have page perform actions based on value of cookie. when page loads, want halt these actions holding shift key.

function checkforshift() {     if (window.event.shiftkey) {         alert('shift key detected, aborting');         return false     }     else {         //do stuff     } } 

this works great, unless call checkforshift() settimeout() function. so:

settimeout ( "checkforshift()" , 500 ); 

in case, checkforshift() function called after 500ms, next line fails message:

unable property 'shiftkey' of undefined or null reference 

why undefined when called settimeout() ?

the event valid when occurs (and don't use window.event provided event handling callback).

to achieve want, must store state detecting changes :

var shiftkeydown = false; window.onkeydown = function(e){     shiftkeydown = !!(e||window.event).shiftkey; } window.onkeyup = function(){     shiftkeydown = false; } function checkforshift() {     if (shiftkeydown) {         alert('shift key detected, aborting');     } else {         //do stuff     } } 

and when call settimeout, don't pass string function :

settimeout (checkforshift , 500 );