find second largest number from an array

var art = [1,5,2,8,3,100,50,250,120,240]
function largest(nul){
emp2 = [0]
emp3 = 0
for(var i=0; i<nul.length; i++){
if(nul[i]>emp2){
emp3=emp2
emp2 = nul[i]
}
else if(nul[i]!==emp2 && nul[i]>emp3){
emp3 = nul[i]
}
}
return emp2
}
console.log(largest(art))