Length, area, center and bounding box

• Use turf.length(route, { units: 'kilometers' }) rather than passing a coordinate array to turf.distance.
• Place labels with turf.centerOfMass or turf.pointOnFeature so they fall inside irregular polygons.
• Convert bbox output with turf.bboxPolygon for clipping or coarse filtering.

var route = turf.lineString([
  [116.391263, 39.907359],
  [116.407000, 39.899000],
  [116.430000, 39.910000]
]);

var km  = turf.length(route, { units: 'kilometers' });
var mi  = turf.length(route, { units: 'miles' });
var deg = turf.length(route, { units: 'degrees' });

console.log(km.toFixed(3), mi.toFixed(3), deg.toFixed(3));

var plot = turf.polygon([[
  [116.380, 39.900],
  [116.400, 39.900],
  [116.400, 39.915],
  [116.380, 39.915],
  [116.380, 39.900]
]]);

var m2  = turf.area(plot);
var km2 = m2 / 1e6;
var ha  = m2 / 1e4;
var mu  = m2 / 666.6667;      // 1 亩 ≈ 666.67 平方米

console.log(m2.toFixed(1), km2.toFixed(4), ha.toFixed(2), mu.toFixed(2));

• Using units: 'degrees' and treating the result as meters is off by about five orders of magnitude.
• Self-intersecting rings skew or even negate the spherical area, so run turf.kinks first.