• 方法一

/* 計算經緯度之間的距離公式 */
function getRad(d) {
	var PI = Math.PI;
	return d * PI / 180.0;
}
/**
 * 獲取兩個經緯度之間的距離：A[lng1,lat1],B[lng2,lat2]
 * @param lng1 A點的經度
 * @param lat1 A點的緯度
 * @param lng2 B點的經度
 * @param lat2 B點的緯度
 * @returns {Number}
 */
function getDistance(lng1, lat1, lng2, lat2) {
	var f = getRad((lat1 + lat2) / 2);
	var g = getRad((lat1 - lat2) / 2);
	var l = getRad((lng1 - lng2) / 2);
	var sg = Math.sin(g);
	var sl = Math.sin(l);
	var sf = Math.sin(f);
	var s, c, w, r, d, h1, h2;
	var a = 6378137.0; // 地球半徑   
	var fl = 1 / 298.257;
	sg = sg * sg;
	sl = sl * sl;
	sf = sf * sf;
	s = sg * (1 - sl) + (1 - sf) * sl;
	c = (1 - sg) * (1 - sl) + sf * sl;
	w = Math.atan(Math.sqrt(s / c));
	r = Math.sqrt(s * c) / w;
	d = 2 * w * a;
	h1 = (3 * r - 1) / 2 / c;
	h2 = (3 * r + 1) / 2 / s;
	s = d * (1 + fl * (h1 * sf * (1 - sg) - h2 * (1 - sf) * sg));
	s = s / 1000;
	s = s.toFixed(18); //指定小數點後的位數。   
	return s;
}
 

• 方法二

  var factors = {
  	miles: 3960,
  	nauticalmiles: 3441.145,
  	degrees: 57.2957795,
  	radians: 1,
  	inches: 250905600,
  	yards: 6969600,
  	meters: 6373000,
  	metres: 6373000,
  	kilometers: 6373,
  	kilometres: 6373
  };
  function PointToDistance(A, B, units) {
  	// A {array} form第一個點經緯度
  	// B {array} to第二個點經緯度
  	var R = Math.PI / 180;
  	var dLat = R * (B[1] - A[1]);
  	var dLon = R * (B[0] - A[0]);
  	var lat1 = R * A[1];
  	var lat2 = R * B[1];
  	var a = Math.pow(Math.sin(dLat / 2), 2) + Math.pow(Math.sin(dLon / 2), 2) * Math.cos(lat1) * Math.cos(lat2);
  	var s = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
  	var factor = factors[units || 'kilometers'];
  	if(factor === undefined) {
  		throw new Error('Invalid unit');
  	}
  	return s * factor;
  }