bbox utils

bbox2geojson.js

/**
 * bbox: [llX, llY, urX, urY]
 * ┌──╗ - ur (2)
 * ╚──┘
 * └ ll (1)
 */
function bboxToPolygon(bbox) {
  const [llX, llY, urX, urY] = bbox;
  return {
    "type": "Feature",
    "properties": {},
    "geometry": {
      "type": "Polygon",
      "coordinates": [
        [
          [ llX, llY ],
          [ llX, urY ],
          [ urX, urY ],
          [ urX, llY ],
          [ llX, llY ]
        ]
      ]
    }
  }
}

function polygonToBbox(feature) {
  if (feature.type === "Polygon") {
     const coordinates = feature.geometry.coordinates[0];
     return [coordinates[0], coordinates[2]];
  } else {
    throw new Error('Only polygon feature supported');
  }
}

joinBbox.js

const isOdd = num => num % 2 === 1;

export function sum(boxes) {
  const lat = [];
  const lng = [];
  
  for (const box of boxes) {
    box.forEach((b, i) => (isOdd(i) ? lng : lat).push(b);
  }

  return [
    Math.min(...lat),
    Math.min(...lng),
    Math.max(...lat),
    Math.max(...lng),
  ]
}