send file & callback

sendFile.js

  function sendFile(option, cb) {
    /* {
      field: name,
      url: '/path/to/upload',
      file: FileObject
    } */
    var field = option.field;
    var xhr = new XMLHttpRequest();
    var fd = new FormData();
    var resp;

    xhr.open("POST", option.url, true);
    xhr.onreadystatechange = function () {
      if (xhr.readyState == 4 && xhr.status == 200) {
        // Handle response.
        resp = JSON.parse(xhr.responseText);
        cb && cb(resp);
      }
    };
    xhr.addEventListener('load', function () {
      resp = JSON.parse(xhr.responseText);
      //cb(resp);
    }, false);

    // send multiple files;
    //var files = Array.apply(null,option.file);
    //files.forEach(function(item) {
    //  fd.append(field, item, item.name);
    //})
    fd.append(field, option.file);

    // Initiate a multipart/form-data upload
    xhr.send(fd);
  }