An example of how to Get Files from a Folder using Ecmascript\Javascript client object model in SharePoint

    <script type=”text/ecmascript”>
    function ViewAllFiles()
    {
    var context = new SP.ClientContext.get_current();
    var web = context.get_web();
    var list = web.get_lists().getByTitle(‘Shared Documents’);
    var query = SP.CamlQuery.createAllItemsQuery();
    query.set_folderServerRelativeUrl(‘/Shared%20Documents/TestFolder’);
    allItems = list.getItems(query);
    context.load(allItems, ‘Include(Title, ContentType, File)’);
    context.executeQueryAsync(Function.createDelegate(this, this.success), Function.createDelegate(this, this.failed));
    }
    function success()
    {
    var fileUrls = “”;
    var ListEnumerator = this.allItems.getEnumerator();
    while(ListEnumerator.moveNext())
    {
    var currentItem = ListEnumerator.get_current();
    var _contentType = currentItem.get_contentType();
    if(_contentType.get_name() != “Folder”)
    {
    var File = currentItem.get_file();
    if(File != null)
    {
    fileUrls += File.get_serverRelativeUrl() + ‘\n';
    }
    }
    }
    alert(fileUrls);
    }
    function failed(sender, args) {
    alert(“failed. Message:” + args.get_message());
    }
    </script>
    <a href=”#” onclick=”Javascript:ViewAllFiles();”>View All Files in Test Folder</a>