function f(arr) {
     if(arr){
      var merged = [];
      return merged.concat.apply(merged, arr).join("")
      }
    }
function f(arr) {
     if(arr){
      var merged = [];
      return merged.concat.apply(merged, arr).join("")
      }
    }
function f ( arr ) { if ( arr ) { var merged = [ ] ; return merged . concat . apply ( merged , arr ) . join ( "" ) } }
flatten an array and join it
flatten an array and join it