Preserve form values across page loads -- i.e. persistent forms. Uses `localStorage` to persist, `jQuery` for utilities.

FormRepo.js

var FormRepo = function (namespace) {
	/// <summary>Persistent form values, saves to localStorage</summary>
	/// <param name="namespace" type="String">the namespace to store values in localStorage</param>

	// should also protect per page, since we could have the same forms in various places
	this.N = namespace + '.' + window.location.pathname;
};
$.extend(FormRepo.prototype, {
	namespace: function (key) {
		return this.N + '.' + key;
	}
	,
	preserve: function ($form, iden) {
		var data = $form.serializeArray();

		localStorage.setItem(this.namespace( 'form.' + (iden || $form.index()) ), JSON.stringify( data ));
	}
	,
	restore: function ($form, iden) {
		var data = localStorage.getItem(this.namespace('form.' + (iden || $form.index())));
		if (null == data || $.isEmptyObject(data)) return; // nothing to do

		$.each(JSON.parse(data), function (i, kv) {
			// find form element, set its value
			var $input = $form.find('[name=' + kv.name + ']');

			// how to set it's value?
			if ($input.is(':checkbox') || $input.is(':radio')) {
				$input.filter(function () { return $(this).val() == kv.value; }).first().attr('checked', 'checked');
			}
			else {
				$input.val(kv.value);
			}
		});
	}//--	fn	restore
	,
	remove: function ($form, iden) {
		localStorage.removeItem(this.namespace('form.' + (iden || $form.index())));
	}//--	fn	remove
	,
	all: function () {
		var allData = {};
		for (var i = 0, l = localStorage.length; i < l; i++) {
			allData[localStorage.key(i)] = localStorage.getItem( localStorage.key(i) );
		}
		return allData;
	}//--	fn	repo.all
});

usage.html

<form id="input" action="#">

<!--
div.field>(label[for=INPUT]{INPUT}+textarea#INPUT[name=INPUT])
div.field>(label[for=INPUT]{INPUT}+input#INPUT[name=INPUT][type=text])
-->

<div class="field wide">
	<label for="url">Url</label>
	<input type="text" name="url" id="url" />
</div>

<div class="field wide">
	<label for="format">Format</label>
	<select id="format" name="format" class="selectControl"
	title="Select form encoding">
	  <option value="">
		Add new...
	  </option>
	  <option value="application/atom+xml">
		application/atom+xml
	  </option>
	  <option value="application/json" selected="selected">
		application/json
	  </option>
	  <option value="application/x-www-form-urlencoded">
		application/x-www-form-urlencoded
	  </option>
	  <option value="application/xml">
		application/xml
	  </option>
	  <option value="multipart/form-data">
		multipart/form-data
	  </option>
	  <option value="text/html">
		text/html
	  </option>
	  <option value="text/plain">
		text/plain
	  </option>
	</select>
</div>

<div class="field">
	<label for="payload">Payload</label>
	<textarea name="payload" id="payload" cols="30" rows="10"></textarea>
</div>

<!--
div.field>fieldset.radios>(legend>(span{Submission Style})+ul>(li.field>(input#submit-regular[name=submission][type=radio][value=regular]+label[for=submit-regular]{Regular}))*2)
-->
<div class="field">
	<fieldset class="radios">
		<legend><span>Submission Style</span></legend>
		<ul>
			<li class="field">
				<input type="radio" id="submit-regular" name="submission" value="regular"/>
				<label for="submit-regular">Regular</label>
			</li>
			<li class="field">
				<input type="radio" id="submit-dotnet" name="submission" value="dotnet" checked="checked" />
				<label for="submit-dotnet">.NET</label>
			</li>
		</ul>
	</fieldset>
</div>

<input type="submit" value="Send" />

<pre id="output">
</pre>

</form>

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.9.0/jquery.min.js"></script>
<script src="FormRepo.js"></script>
<script>
	var $form = $('#input')
		, $output = $('#output')
		, repo = new FormRepo('restclient')
		;

	// get the last submitted values back
	repo.restore($form/*, $form.attr('id')*/ ); // don't necessarily need an identifier

	$form.submit(function (e) {
		// preserve the last submitted values
		repo.preserve($form/*, $form.attr('id')*/ ); // don't necessarily need an identifier
	});
	
	console.log( repo.all() );
</script>

Hi,
thanks for this but when I follow your usage example on Firefox 45.01 using jQuery 1.11 I get the following error:

"TypeError: FormRepo is not a constructor" pointing to the following line in your example:
, repo = new FormRepo('restclient') as the culprit.

Any clues?

Beautiful, you save me a lot of time, ty very much

This script is nice! Unfortunately I wrote my own before finding yours.

In case anyone is interested: https://github.com/FThompson/FormPersistence.js

Any idea on how to make this work for multiselect fields? In chrome, the js works as expected, but in Firefox (77.0.1), only the last item of the multiselect is retained, the other options are dropped even though they are in localStorage.