browser.js

var xhr = require('xhr')
var noop = function(){}
var parseASCII = require('parse-bmfont-ascii')
var parseXML = require('parse-bmfont-xml')
var readBinary = require('parse-bmfont-binary')
var isBinaryFormat = require('./lib/is-binary')
var xtend = require('xtend')

var xml2 = (function hasXML2() {
  return self.XMLHttpRequest && "withCredentials" in new XMLHttpRequest
})()

module.exports = function(opt, cb) {
  cb = typeof cb === 'function' ? cb : noop

  if (typeof opt === 'string')
    opt = { uri: opt }
  else if (!opt)
    opt = {}

  var expectBinary = opt.binary
  if (expectBinary)
    opt = getBinaryOpts(opt)

  xhr(opt, function(err, res, body) {
    if (err)
      return cb(err)
    if (!/^2/.test(res.statusCode))
      return cb(new Error('http status code: '+res.statusCode))
    if (!body)
      return cb(new Error('no body result'))

    var binary = false 

    //if the response type is an array buffer,
    //we need to convert it into a regular Buffer object
    if (isArrayBuffer(body)) {
      var array = new Uint8Array(body)
      body = Buffer.from(array, 'binary')
    }

    //now check the string/Buffer response
    //and see if it has a binary BMF header
    if (isBinaryFormat(body)) {
      binary = true
      //if we have a string, turn it into a Buffer
      if (typeof body === 'string') 
        body = Buffer.from(body, 'binary')
    } 

    //we are not parsing a binary format, just ASCII/XML/etc
    if (!binary) {
      //might still be a buffer if responseType is 'arraybuffer'
      if (Buffer.isBuffer(body))
        body = body.toString(opt.encoding)
      body = body.trim()
    }

    var result
    try {
      var type = res.headers['content-type']
      if (binary)
        result = readBinary(body)
      else if (/json/.test(type) || body.charAt(0) === '{')
        result = JSON.parse(body)
      else if (/xml/.test(type)  || body.charAt(0) === '<')
        result = parseXML(body)
      else
        result = parseASCII(body)
    } catch (e) {
      cb(new Error('error parsing font '+e.message))
      cb = noop
    }
    cb(null, result)
  })
}

function isArrayBuffer(arr) {
  var str = Object.prototype.toString
  return str.call(arr) === '[object ArrayBuffer]'
}

function getBinaryOpts(opt) {
  //IE10+ and other modern browsers support array buffers
  if (xml2)
    return xtend(opt, { responseType: 'arraybuffer' })
  
  if (typeof self.XMLHttpRequest === 'undefined')
    throw new Error('your browser does not support XHR loading')

  //IE9 and XML1 browsers could still use an override
  var req = new self.XMLHttpRequest()
  req.overrideMimeType('text/plain; charset=x-user-defined')
  return xtend({
    xhr: req
  }, opt)
}