overpass-frontend/src/httpLoad.js

A JavaScript (NodeJS/Browser) library to easily access data from OpenStreetMap via Overpass API or from an OSM File. The objects can directly be used with LeafletJS or exported to GeoJSON. Data will be cached in the browser memory.

/* global location:false */

if (typeof XMLHttpRequest === 'undefined') {
  global.XMLHttpRequest = require('xmlhttprequest').XMLHttpRequest
}

function httpLoad (url, getParam, postParam, callback) {
  const req = new global.XMLHttpRequest()

  req.onreadystatechange = function () {
    let data = null
    let err = null

    if (req.readyState === 4) {
      if (req.status === 200) {
        try {
          data = JSON.parse(req.responseText)
        } catch (err) {
          // err already set
        }

        callback(err, data)
      } else {
        try {
          err = new Error(JSON.parse(req.responseText))
        } catch (err) {
          if (req.responseText.search('OSM3S Response') !== -1) {
            const lines = req.responseText.split(/\n/)
            let e = ''

            for (let i = 0; i < lines.length; i++) {
              const m = lines[i].match(/<p><strong style="color:#FF0000">Error<\/strong>: (.*)<\/p>/)
              if (m) {
                e += m[1] + '\n'
              }
            }

            // Could not parse error message - create alternative
            if (e === '') {
              e = 'Got error ' + req.status
            }

            const error = new Error(e)
            error.status = req.status

            callback(error, null)
          } else {
            const error = new Error(req.responseText)
            error.status = req.status

            callback(error, null)
          }
        }
      }
    }
  }

  let reqType = 'GET'
  let postData = null
  if (postParam) {
    reqType = 'POST'
    postData = postParam
  }

  if (url.substr(0, 2) === '//') {
    if (typeof location === 'undefined') {
      url = 'https:' + url
    } else {
      url = location.protocol + url
    }
  }

  req.open(reqType, url, true)
  try {
    req.send(postData)
  } catch (err) {
    callback(err, null)
  }
}

module.exports = httpLoad