objFromForm.js is a small set of javascript to populate and restore a form to Javascript objects — and therefore JSON.

objFromForm.js

// [© 2012 Bellite.io](http://bellite.io)
// Open Source as [CC BY-SA 3.0](http://creativecommons.org/licenses/by-sa/3.0/)
// vim: sw=2 ts=2 expandtab
(function(exports) {
  "use strict";
  function objFromForm(form, dispatch) {
    if (!form || form.nodeName!="FORM") return;
    dispatch = dispatch || objFromForm.dispatch
    var res={}, elem, fn

    function set(elem, value) {
      res[elem.name] = value===undefined ? elem.value : value }

    for (var i=0; i<form.elements.length; i++) {
      elem = form.elements[i];
      if (elem.name) {
        fn = (elem.nodeName=='INPUT' ? elem.type : elem.nodeName)
        fn = (dispatch[fn] || dispatch.assign)
        fn(elem, set)
      }
    }
    return res }
  objFromForm.dispatch = {
    checkbox: function(elem, set) {
      set(elem, !!elem.checked) },
    radio: function(elem, set) {
      if (elem.checked) set(elem) },
    SELECT: function(elem, set) {
      if (elem.type=='select-one')
          return set(elem)
      var ans=[]
      for (var i=0; i<elem.options.length; i++)
          if (elem.options[i].selected)
              ans.push(elem.options[i].value)
      set(elem, ans) },
    assign: function(elem, set) { set(elem) }}

  function formFromObj(form, obj, dispatch) {
    if (!form || form.nodeName!="FORM") return;
    dispatch = dispatch || formFromObj.dispatch
    var elem, key, fn,
        names = Object.keys(obj)

    for (var i=0; i<names.length; i++) {
      elem = form[names[i]]
      if (elem!==undefined) {
        fn = (elem.nodeName=='INPUT' ? elem.type : elem.nodeName)
        fn = (dispatch[fn] || dispatch.assign)
        fn(elem, obj[names[i]])
      }
    }
    return form }
  formFromObj.dispatch = {
    checkbox: function(elem, value) {
      elem.checked = !!value },
    radio: function(elem, value) {
      if (elem.value == value)
        elem.checked = true },
    SELECT: function(elem, valueList) {
      valueList = [].concat(valueList)
      if (elem.type=='select-one')
          return elem.value = valueList[0]
      for (var i=0,opt; i<elem.options.length; i++) {
        opt = elem.options[i]
        opt.selected = 0<=valueList.indexOf(opt.value)
      }},
    assign: function assign(elem, value) {
      elem.value = value }}

  exports.objFromForm = objFromForm
  exports.formFromObj = formFromObj
  return exports;
})(this)