document.getElementById(c).onclick=function() { kek(m,num); }
<!DOCTYPE HTML> <html> <head> <title>Untitled</title> <meta charset="utf-8"> <style type="text/css"> #box { width:59px; height:40px; background-color:#6B86A6; border-radius: 8px; text-align: center; color: #FFFF00; } </style> </head> <body> <div id="box" class="footer">жмак</div> <script> var c = "box", m = "фигня", num = "всякая", kek = function(a, b) { alert(a+" "+b+"!") }; document.getElementById(c).onclick=function() { kek(m,num); } </script> </body> </html>