var points = turf.featurecollection([
  turf.point([5,5], {population: 5}),
  turf.point([1,3], {population: 40}),
  turf.point([14,2], {population: 80}),
  turf.point([13,1], {population: 90}),
  turf.point([19,7], {population: 100})
]);
 
var breaks = turf.quantile(
  points, 'population', [25, 50, 75, 99]);
 
//=breaks