JavaScript 取得座標位址

內容開始

已經是很公開的標準了，資料多到不行～～ 還是筆記一下

取得座標 - getCurrentPosition

MDN Doc

const successCallback = (position) => {
    // position.coords.latitude 緯度
    // position.coords.longitude 精度
    // position.timestamp 取得的時間戳 ex:1624703519728 
}

const errorCallback = (err) => {
    // err.code 列表
    // err.PERMISSION_DENIED: 1
    // err.POSITION_UNAVAILABLE: 2
    // err.TIMEOUT: 3
    if (err.code === err.PERMISSION_DENIED) {
        console.log('你就是沒開嘛')
    }
}

const options = {
    // false | true
    enableHighAccuracy: true,

    // integer (milliseconds)
    // amount of time before the error callback is invoked, 
    // if 0 it will never invoke.
    timeout: 5000,

    // integer (milliseconds)
    // infinity - maximum cached position age.
    maximumAge: 0
}

navigator.geolocation.getCurrentPosition(successCallback, errorCallback, options)

定期查看座標 - watchPosition

MDN Doc

// 會回傳一個 id 用來取消 watch，其它用法跟 getCurrentPosition 一樣的
const wid = navigator.geolocation.watchPosition(successCallback, errorCallback, options)

// 這樣子關～
navigator.geolocation.clearWatch(wid)

確認權限

有時候會想要檢查權限現在的狀態

navigator.permissions.query({ name: 'geolocation' })
  .then(result => {
    // result.state 有三種
    // granted 允許
    // prompt 要詢問
    // denied 封鎖
  })

計算兩點之間的距離

感覺會放在一起用～ 筆記起來

const getDistance = (lat1, lng1, lat2, lng2, unit) => {
  const radLat1 = (Math.PI * lat1) / 180
  const radLat2 = (Math.PI * lat2) / 180
  const theta = lng1 - lng2
  const radTheta = (Math.PI * theta) / 180
  let dist = Math.sin(radLat1) * Math.sin(radLat2)
    + Math.cos(radLat1) * Math.cos(radLat2) * Math.cos(radTheta)
  if (dist > 1) {
    dist = 1
  }
  dist = Math.acos(dist)
  dist = (dist * 180) / Math.PI
  dist = dist * 60 * 1.1515
  if (unit === 'K') { dist *= 1.609344 }
  if (unit === 'N') { dist *= 0.8684 }
  return dist // 'M' is statute miles (default)
}

Ref

https://www.pluralsight.com/guides/how-to-use-geolocation-call-in-reactjs https://developer.mozilla.org/zh-TW/docs/Web/API/Navigator/geolocation