gistfile1.txt

var start = 5000;
var end = 21000;
var position = 5072;
var percentThere = (position-start)/(end-start);
var count = 300;
var mark = percentThere * count;
var a = "[";
for (var x = 0; x <= count; x++) {
  if (x < mark) {
    a += "*"
  } else {
    a += "-";
  }
}
a += "]";
console.log(a);