Setting array between two coords. https://github.com/duncancumming/maps/blob/master/animatedPaths/1.html

getPathCoords.js

const posFrom = { 'lat': 35.799465, 'lng': 138.356991 }
const posTo   = { 'lat': 35.801618, 'lng': 138.355843 }
const frame   = 110
let pathCoords = []

for(let i = 0; i < frame; i++) {
  pathCoords.push({ 'lat': (posFrom.lat + ((posTo.lat - posFrom.lat) / frame) * i)
              , 'lng': (posFrom.lng + ((posTo.lng - posFrom.lng) / frame) * i) })
}
/*
for (let i = 0; i < pathCoords.length; i++) {
  setTimeout((pathCoords) => {
    moveMarker(map, marker, pathCoords.lat, pathCoords.lng)
  }, frame * i, pathCoords[i])
}
*/