Javascript 在js循环中获取上一个和当前光标的差异

// https://stackoverflow.com/a/27943/28004
function getDistanceFromLatLonInKm(lat1,lon1,lat2,lon2) {
  var R = 6371; // Radius of the earth in km
  var dLat = deg2rad(lat2-lat1);  // deg2rad below
  var dLon = deg2rad(lon2-lon1); 
  var a = 
    Math.sin(dLat/2) * Math.sin(dLat/2) +
    Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2)) * 
    Math.sin(dLon/2) * Math.sin(dLon/2)
    ; 
  var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a)); 
  var d = R * c; // Distance in km
  return d;
}

function deg2rad(deg) {
  return deg * (Math.PI/180)
}
// end of pasted code

// your entry
const points = [
    [51.06745252933975, -114.11267548799515],
    [51.067506465746014, -114.09559518098831],
    [51.0827140244322,-114.0949085354805],
    [51.088267312195484,-114.10709649324417]
]

// looping through all points starting from the second element
for (let i = 1; i < points.length; i += 1) {
  const lastPosition = points[i-1];
  const newPosition = points[i];
  console.log(
      `from position ${i-1} to ${i} it's %s Km`,
      getDistanceFromLatLonInKm(lastPosition[0], lastPosition[1], newPosition[0], newPosition[1]))
}