Remembers form state on reload

index.js

function remember(form) {
  var map = function (subject, fn) {
    [].map.call(subject, fn);
  };

  if (!form) {
    [].map(document.forms, remember);
    return;
  }

  var checkboxes = {};
  var store = sessionStorage;

  function getValue(node) {
    if (node.nodeName === 'SELECT' && node.multiple) {
      // yay
      if (node.selectedOptions.length) {
        return [].map.call(node.selectedOptions, function (option) {
          return option.value;
        });
      } else {
        return '';
      }
    } else if (node.type === 'checkbox') {
      return ',' + checkboxes[node.name].filter(function (node) {
        return node.checked;
      }).map(function (node) {
        return node.value;
      }).join(',') + ',';
    } else {
      return node.value;
    }
  }

  for (var i = 0, field; field = form[i], i < form.length; i++) {
    if (field.type === 'password') {
      continue; // don't store passwords
    }

    if (field.type === 'checkbox') {
      if (!checkboxes[field.name]) {
        checkboxes[field.name] = [];
      }
      checkboxes[field.name].push(field);
    }

    // radio & checkboxes are handled differently
    var value = store[field.name];

    if (field.nodeName === 'SELECT' && field.multiple) {
      value = ',' + value + ',';
      [].map.call(field.options, function (option) {
        if (value.indexOf(option.value) !== -1) {
          option.selected = true;
        }
      });
    } else if (field.type === 'checkbox' && value) {
      field.checked = (value.indexOf(',' + field.value + ',') !== -1);
    } else if (field.type === 'radio') {
      field.checked = value === field.value;
    } else {
      field.value = value || '';
    }

    field.addEventListener('change', function () {
      store[this.name] = getValue(this);
    }, false);
  }
}