LocalStorage Example: Storing Previous Searches

I've made it clear that I'm a huge fan of LocalStorage. While sitting in the Houston airport for many hours this week, I decided to whip up a little example that demonstrates one of the practical uses for this feature. I built a simple Ajax-based search page and then added LocalStorage as a way to remember your previous searches. This isn't anything special, but I think it's another good example of the feature. Let's begin by taking a look at the application before any use of LocalStorage.

The application makes use of Bootstrap, jQuery, and Handlebars, but for now, let's just focus on the JavaScript and the template:

<script>
    $(document).ready(function() {

      var source = $("#artResultsTemplate").html();
      var template = Handlebars.compile(source);

      $("#searchButton").on("click", function(e) {
        e.preventDefault();
        var search = $.trim($("#search").val());
        if(search === '') return;
        console.log("search for "+search);
        $.get("service.cfc?method=searchArt", {term:search}, function(res,code) {

          var html = template({results:res});
          $("#results").html(html);
        },"JSON");

      });
    });
    </script>

  <script id="artResultsTemplate" type="text/x-handlebars-template">
    <h1>Results</h1>
    {{#if results}}
      <ul class="thumbnails">
      {{#each results}}
        <li class="span3">
          <div class="thumbnail">
            <img src="{{image}}" width="260" height="180" title="{{name}}">
            <div class="caption">
              <h5>{{name}}</h5>
              <p>{{description}}</p>
              <p>Created by {{artist}} and selling for ${{price}}</p>
            </div>
          </div>
        </li>
      {{/each}}
      </ul>
    {{else}}
      <p>
      Sorry, no results.
      </p>
    {{/if}}
  </script>

You can see that I begin by compiling my Handlebars template (this is used for the results), and then I define my click handler for the search button. All the handler does is grab the search string, pass it to a ColdFusion service that hits the database, and then passes the results to my Handlebars template.

Beautiful - and the code is rather simple. You can test this yourself here: http://www.raymondcamden.com/demos/2012/jul/13/test1.html I'd recommend searching for oil, moon, paint, and beer.

Ok, now let's talk about the next version. The updated version will use LocalStorage to remember your last five searches. I decided on five mostly because it just felt right. I thought ten might be a bit much.

To store the last five values, I'll use an array. You can't store complex variables in LocalStorage, but you can easily serialize them with JSON. So for example:

var pastSearches = [];

if(localStorage["pastSearches"]) {
     pastSearches = JSON.parse(localStorage["pastSearches"]);
}

That isn't too complex, is it? Storing the value isn't too hard either. I do a check to see if the value exists in the array, and if not, put it in the front and pop one off the end if the array is too big.

if(pastSearches.indexOf(search) == -1) {
     pastSearches.unshift(search);
     if(pastSearches.length > 5) {
        pastSearches.pop();
     }
     localStorage["pastSearches"] = JSON.stringify(pastSearches);
}

 All that's left then is to simply write out the past searches and listen for click events on them.

function drawPastSearches() {
    if(pastSearches.length) {
        var html = pastSearchesTemplate({search:pastSearches});
        $("#pastSearches").html(html);
    }
}

$(document).on("click", ".pastSearchLink", function(e) {
    e.preventDefault();
    var search = $(this).text();
    doSearch(search);
});

 And voila - I can now remember your last five searches and provide an easy way for you to quickly rerun them. The code samples above are only the most important bits. I encourage you to View Source on the updated version for the complete example. (The ColdFusion code is just a simple query API. You can view that template here.)