[walik]

function in_array(what, where) {
    for(var i=0; i<where.length; i++)
        if(what == where[i]) 
            return true;
    return false;
}
var zip = [1,2,3,4,5,6,7,8,50,48,77];
var value = 50;
if (in_array(value, zip))
   alert('ok');
else
   alert('no');