mergeSort

Example:

// Assume array contains BoundingSpheres in world coordinates.
// Sort them in ascending order of distance from the camera.
const position = camera.positionWC;
Cesium.mergeSort(array, function(a, b, position) {
    return Cesium.BoundingSphere.distanceSquaredTo(b, position) - Cesium.BoundingSphere.distanceSquaredTo(a, position);
}, position);