group consecutive numbers in array , in Javascript.

consecutive_numbers

/*TODO MAKE IT IN ES6
var data=[4,5,6,9,10,14,15,20,21,22,23,24,25,30,31,34]
output
4-6,9-10,14-15,20-25,30-31,34
*/
var data=[4,5,6,9,10,14,15,20,21,22,23,24,25,30,31,34,36,37,94,95];
var start=data[0];
var temp=1;
var a=0;

cons(start,temp);

function cons(s,t){
  if(s+1==data[t]){
    s=data[t];
    t=t+1;
    cons(s,t);
}
else{
    print(a,t-1);
}
}

function print(k,t){
    display(k,t);
    t++;
    a=t;
    start=data[t];
if(t<data.length){cons(start,t+1)}
}
function display(k,t){
    if(k!=t){
    console.log(data[k]+'-'+data[t]);}
else{
    console.log(data[k]);
}
}