transit

transit.js

var distance = require('euclidean-distance')

var lerp = require('lerp')

var pts = [[0, 0], [1, 4], [2, 9], [3, 2], [2, 0]]

//console.log(pts)

var distances = []
var sum = []
var total = 0

sum[0] = 0
distances[0] = 0

for (var i = 1, n = pts.length; i < n; i++) {
  distances[i] = distance(pts[i - 1], pts[i])

  total += distances[i]

  sum[i] = total
}

var d

for (var t = 0.0; t <= 1.0; t += 0.01) {
  d = total * t

  for (var j = 0, m = sum.length - 1; j < m; j++) {
    if ((d >= sum[j]) && (d <= sum[j + 1])) {
      break
    }
  }

  var pt = pts[j]

  var x1 = pt[0]
  var y1 = pt[1]

  var pt = pts[j + 1]

  var x2 = pt[0]
  var y2 = pt[1]

  var x = lerp(x1, x2, (d - sum[j]) / distances[j + 1])
  var y = lerp(y1, y2, (d - sum[j]) / distances[j + 1])

  console.log(x, y)
}