The window.onload append function is used as an example

 
<script type="text/javascript"> 
function tt1(){ 
alert('tt1') ; 
} 
function tt2(){ 
alert('tt2') ; 
} 
function tt3(){ 
alert('tt3') ; 
} 
function addLoadEvent(func) { 
var oldonload = window.onload; 
if (typeof window.onload != 'function') { 
window.onload = func; 
} else { 
window.onload = function() { 
oldonload(); 
func(); 
} 
} 
} 
addLoadEvent(tt1()) ; 
addLoadEvent(tt2()) ; 
addLoadEvent(tt3()) ; 
</script>