docs/data/dataset.html

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  <h1>DataSet</h1>

  <h2 id="Contents">Contents</h2>
  <ul>
    <li><a href="#Overview">Overview</a></li>
    <li><a href="#Example">Example</a></li>
    <li><a href="#Construction">Construction</a></li>
    <li><a href="#Methods">Methods</a></li>
    <li><a href="#Properties">Properties</a></li>
    <li><a href="#Subscriptions">Subscriptions</a></li>
    <li><a href="#Data_Manipulation">Data Manipulation</a></li>
    <li><a href="#Data_Selection">Data Selection</a></li>
  </ul>


  <h2 id="Overview">Overview</h2>

  <p>
    Vis.js comes with a flexible DataSet, which can be used to hold and
    manipulate unstructured data and listen for changes in the data.
    The DataSet is key/value based. Data items can be added, updated and
    removed from the DataSet, and one can subscribe to changes in the DataSet.
    The data in the DataSet can be filtered and ordered, and fields (like
    dates) can be converted to a specific type. Data can be normalized when
    appending it to the DataSet as well.
  </p>


  <h2 id="Example">Example</h2>

  <p>
    The following example shows how to use a DataSet.
  </p>

<pre class="prettyprint lang-js">
// create a DataSet
var options = {};
var data = new vis.DataSet(options);

// add items
// note that the data items can contain different properties and data formats
data.add([
  {id: 1, text: 'item 1', date: new Date(2013, 6, 20), group: 1, first: true},
  {id: 2, text: 'item 2', date: '2013-06-23', group: 2},
  {id: 3, text: 'item 3', date: '2013-06-25', group: 2},
  {id: 4, text: 'item 4'}
]);

// subscribe to any change in the DataSet
data.on('*', function (event, properties, senderId) {
  console.log('event', event, properties);
});

// update an existing item
data.update({id: 2, group: 1});

// remove an item
data.remove(4);

// get all ids
var ids = data.getIds();
console.log('ids', ids);

// get a specific item
var item1 = data.get(1);
console.log('item1', item1);

// retrieve a filtered subset of the data
var items = data.get({
  filter: function (item) {
    return item.group == 1;
  }
});
console.log('filtered items', items);

// retrieve formatted items
var items = data.get({
  fields: ['id', 'date'],
  type: {
    date: 'ISODate'
  }
});
console.log('formatted items', items);
</pre>


  <h2 id="Construction">Construction</h2>

  <p>
    A DataSet can be constructed as:
  </p>

<pre class="prettyprint lang-js">
var data = new vis.DataSet([data] [, options])
</pre>

  <p>
    After construction, data can be added to the DataSet using the methods
    <code>add</code> and <code>update</code>, as described in section
    <a href="#Data_Manipulation">Data Manipulation</a>.
  </p>

  <p>
    The parameter <code>data</code> is optional and is an Array with items.
  </p>

  <p>
    The parameter <code>options</code> is optional and is an object which can
    contain the following properties:
  </p>

  <table class="options">
    <tr>
      <th>Name</th>
      <th>Type</th>
      <th>Default value</th>
      <th>Description</th>
    </tr>
    <tr>
      <td>fieldId</td>
      <td>String</td>
      <td>"id"</td>
      <td>
        The name of the field containing the id of the items.

        When data is fetched from a server which uses some specific
        field to identify items, this field name can be specified
        in the DataSet using the option <code>fieldId</code>.
        For example <a href="http://couchdb.apache.org/"
                       target="_blank">CouchDB</a> uses the field
        <code>"_id"</code> to identify documents.
      </td>
    </tr>
    <tr>
      <td>type</td>
      <td>Object.&lt;String,&nbsp;String&gt;</td>
      <td>none</td>
      <td>
        An object containing field names as key, and data types as
        value. By default, the type of the properties of items are left
        unchanged. Item properties can be normalized by specifying a
        field type. This is useful for example to automatically convert
        stringified dates coming from a server into JavaScript Date
        objects. The available data types are listed in section
        <a href="#Data_Types">Data Types</a>.
      </td>
    </tr>
    <tr>
      <td>queue</td>
      <td>Object | boolean</td>
      <td>none</td>
      <td>
        Queue data changes ('add', 'update', 'remove') and flush them at once.
        The queue can be flushed manually by calling
        <code>DataSet.flush()</code>, or can be flushed after a configured delay
        or maximum number of entries.
        <br>
        <br>
        When <code>queue</code> is true, a queue is created
        with default options. Options can be specified by providing an object:
        <ul>
          <li><code>delay: number</code><br>
            The queue will be flushed automatically after an inactivity of this
            delay in milliseconds. Default value is <code>null</code>.
          <li><code>max: number</code><br>
            When the queue exceeds the given maximum number
            of entries, the queue is flushed automatically.
            Default value is <code>Infinity</code>.
          </li>
        </ul>
      </td>
    </tr>
  </table>


  <h2 id="Methods">Methods</h2>

  <p>DataSet contains the following methods.</p>

  <table class="methods">
    <tr>
      <th>Method</th>
      <th>Return Type</th>
      <th>Description</th>
    </tr>

    <tr>
      <td>add(data [, senderId])</td>
      <td>Number[]</td>
      <td>Add one or multiple items to the DataSet. <code>data</code> can be a single item or an array with items. Adding an item will fail when there already is an item with the same id. The function returns an array with the ids of the added items. See section <a href="#Data_Manipulation">Data Manipulation</a>.</td>
    </tr>

    <tr>
      <td>clear([senderId])</td>
      <td>Number[]</td>
      <td>Clear all data from the DataSet. The function returns an array with the ids of the removed items.</td>
    </tr>

    <tr>
      <td>distinct(field)</td>
      <td>Array</td>
      <td>Find all distinct values of a specified field. Returns an unordered array containing all distinct values. If data items do not contain the specified field are ignored.</td>
    </tr>

    <tr>
      <td>flush()</td>
      <td>none</td>
      <td>Flush queued changes. Only available when the DataSet is configured with the option <code>queue</code>, see section <a href="#Construction">Construction</a>.</td>
    </tr>

    <tr>
      <td>forEach(callback&nbsp;[,&nbsp;options])</td>
      <td>none</td>
      <td>
        Execute a callback function for every item in the dataset.
        The available options are described in section <a href="#Data_Selection">Data Selection</a>.
      </td>
    </tr>

    <tr>
      <td>
        get([options] [, data])<br>
        get(id [,options] [, data])<br>
        get(ids [, options] [, data])
      </td>
      <td>Object | Array</td>
      <td>
        Get a single item, multiple items, or all items from the DataSet.
        Usage examples can be found in section <a href="#Getting_Data">Getting Data</a>, and the available <code>options</code> are described in section <a href="#Data_Selection">Data Selection</a>. When no item is found, <code>null</code> is returned when a single item was requested, and and empty Array is returned in case of multiple id's.
      </td>
    </tr>

    <tr>
      <td>
        getDataSet()
      </td>
      <td>DataSet</td>
      <td>
        Get the DataSet itself. In case of a DataView, this function does not
        return the DataSet to which the DataView is connected.
      </td>
    </tr>

    <tr>
      <td>
        getIds([options])
      </td>
      <td>Number[]</td>
      <td>
        Get ids of all items or of a filtered set of items.
        Available <code>options</code> are described in section <a href="#Data_Selection">Data Selection</a>, except that options <code>fields</code> and <code>type</code> are not applicable in case of <code>getIds</code>.
      </td>
    </tr>

    <tr>
      <td>map(callback [, options])</td>
      <td>Array</td>
      <td>
        Map every item in the DataSet.
        The available options are described in section <a href="#Data_Selection">Data Selection</a>.
      </td>
    </tr>

    <tr>
      <td>max(field)</td>
      <td>Object | null</td>
      <td>
        Find the item with maximum value of specified field. Returns <code>null</code> if no item is found.
      </td>
    </tr>

    <tr>
      <td>min(field)</td>
      <td>Object | null</td>
      <td>
        Find the item with minimum value of specified field. Returns <code>null</code> if no item is found.
      </td>
    </tr>

    <tr>
      <td>off(event, callback)</td>
      <td>none</td>
      <td>
        Unsubscribe from an event, remove an event listener. See section <a href="#Subscriptions">Subscriptions</a>.
      </td>
    </tr>

    <tr>
      <td>on(event, callback)</td>
      <td>none</td>
      <td>
        Subscribe to an event, add an event listener. See section <a href="#Subscriptions">Subscriptions</a>.
      </td>
    </tr>

    <tr>
      <td>
        remove(id [, senderId])<br>
        remove(ids [, senderId])
      </td>
      <td>Number[]</td>
      <td>
        Remove one or multiple items by id or by the items themselves. Returns an array with the ids of the removed items. See section <a href="#Data_Manipulation">Data Manipulation</a>.
      </td>
    </tr>

    <tr>
      <td>
        setOptions(options)
      </td>
      <td>none</td>
      <td>
        Set options for the DataSet. Available options:

        <ul>
          <li>
            <code>queue</code><br>
            Queue data changes ('add', 'update', 'remove') and flush them at once.
            The queue can be flushed manually by calling
            <code>DataSet.flush()</code>, or can be flushed after a configured delay
            or maximum number of entries.
            <br>
            <br>
            When <code>queue</code> is true, a queue is created with default options.
            When <code>queue</code> is false, an existing queue will be flushed and removed.
            Options can be specified by providing an object:
            <ul>
              <li><code>delay: number</code><br>
                The queue will be flushed automatically after an inactivity of this
                delay in milliseconds. Default value is <code>null</code>.
              <li><code>max: number</code><br>
                When the queue exceeds the given maximum number
                of entries, the queue is flushed automatically.
                Default value is <code>Infinity</code>.
              </li>
            </ul>
          </li>
        </ul>
      </td>
    </tr>

    <tr>
      <td>
        update(data [, senderId])
      </td>
      <td>Number[]</td>
      <td>
        Update one or multiple existing items. <code>data</code> can be a single item or an array with items. When an item doesn't exist, it will be created. Returns an array with the ids of the removed items. See section <a href="#Data_Manipulation">Data Manipulation</a>.
      </td>
    </tr>

  </table>


  <h2 id="Properties">Properties</h2>

  <p>DataSet contains the following properties.</p>

  <table>
    <tr>
      <th>Property</th>
      <th>Type</th>
      <th>Description</th>
    </tr>

    <tr>
      <td>length</td>
      <td>Number</td>
      <td>The number of items in the DataSet.</td>
    </tr>
  </table>


  <h2 id="Subscriptions">Subscriptions</h2>

  <p>
    One can subscribe on changes in a DataSet.
    A subscription can be created using the method <code>on</code>,
    and removed with <code>off</code>.
  </p>

<pre class="prettyprint lang-js">
// create a DataSet
var data = new vis.DataSet();

// subscribe to any change in the DataSet
data.on('*', function (event, properties, senderId) {
  console.log('event:', event, 'properties:', properties, 'senderId:', senderId);
});

// add an item
data.add({id: 1, text: 'item 1'});              // triggers an 'add' event
data.update({id: 1, text: 'item 1 (updated)'}); // triggers an 'update' event
data.remove(1);                                 // triggers an 'remove' event
</pre>


  <h3 id="On">On</h3>

  <p>
    Subscribe to an event.
  </p>

  Syntax:
  <pre class="prettyprint lang-js">DataSet.on(event, callback)</pre>

  Where:
  <ul>
    <li>
      <code>event</code> is a String containing any of the events listed
      in section <a href="#Events">Events</a>.
    </li>
    <li>
      <code>callback</code> is a callback function which will be called
      each time the event occurs. The callback function is described in
      section <a href="#Callback">Callback</a>.
    </li>
  </ul>

  <h3 id="Off">Off</h3>

  <p>
    Unsubscribe from an event.
  </p>

  Syntax:
  <pre class="prettyprint lang-js">DataSet.off(event, callback)</pre>

  Where <code>event</code> and <code>callback</code> correspond with the
  parameters used to <a href="#On">subscribe</a> to the event.

  <h3 id="Events">Events</h3>

  <p>
    The following events are available for subscription:
  </p>

  <table>
    <tr>
      <th>Event</th>
      <th>Description</th>
    </tr>
    <tr>
      <td>add</td>
      <td>
        The <code>add</code> event is triggered when an item
        or a set of items is added, or when an item is updated while
        not yet existing.
      </td>
    </tr>
    <tr>
      <td>update</td>
      <td>
        The <code>update</code> event is triggered when an existing item
        or a set of existing items is updated.
      </td>
    </tr>
    <tr>
      <td>remove</td>
      <td>
        The <code>remove</code> event is triggered when an item
        or a set of items is removed.
      </td>
    </tr>
    <tr>
      <td>*</td>
      <td>
        The <code>*</code> event is triggered when any of the events
        <code>add</code>, <code>update</code>, and <code>remove</code>
        occurs.
      </td>
    </tr>
  </table>

  <h3 id="Callback">Callback</h3>

  <p>
    The callback functions of subscribers are called with the following
    parameters:
  </p>

    <pre class="prettyprint lang-js">
function (event, properties, senderId) {
  // handle the event
});
</pre>

  <p>
    where the parameters are defined as
  </p>

  <table>
    <tr>
      <th>Parameter</th>
      <th>Type</th>
      <th>Description</th>
    </tr>
    <tr>
      <td>event</td>
      <td>String</td>
      <td>
        Any of the available events: <code>add</code>,
        <code>update</code>, or <code>remove</code>.
      </td>
    </tr>
    <tr>
      <td>properties</td>
      <td>Object&nbsp;|&nbsp;null</td>
      <td>
        Optional properties providing more information on the event.
        In case of the events <code>add</code>,
        <code>update</code>, and <code>remove</code>,
        <code>properties</code> is always an object containing a property
        <code>items</code>, which contains an array with the ids of the affected
        items. The <code>update</code> and <code>remove</code> events have an extra
        field <code>oldData</code> containing the original data of the items in the
        dataset before the items were updated or removed. The <code>update</code>
        event also contains a field <code>data</code> containing the changes:
        the properties of the items that are being updated. 
      </td>
    </tr>
    <tr>
      <td>senderId</td>
      <td>String&nbsp;|&nbsp;Number</td>
      <td>
        An senderId, optionally provided by the application code
        which triggered the event. If senderId is not provided, the
        argument will be <code>null</code>.
      </td>
    </tr>
  </table>


  <h2 id="Data_Manipulation">Data Manipulation</h2>

  <p>
    The data in a DataSet can be manipulated using the methods
    <a href="#Add"><code>add</code></a>,
    <a href="#Update"><code>update</code></a>,
    and <a href="#Remove"><code>remove</code></a>.
    The DataSet can be emptied using the method
    <a href="#Clear"><code>clear</code></a>.
  </p>

<pre class="prettyprint lang-js">
// create a DataSet
var data = new vis.DataSet();

// add items
data.add([
  {id: 1, text: 'item 1'},
  {id: 2, text: 'item 2'},
  {id: 3, text: 'item 3'}
]);

// update an item
data.update({id: 2, text: 'item 2 (updated)'});

// remove an item
data.remove(3);
</pre>

  <h3 id="Add">Add</h3>

  <p>
    Add a data item or an array with items.
  </p>

  Syntax:
  <pre class="prettyprint lang-js">var addedIds = DataSet.add(data [, senderId])</pre>

  The argument <code>data</code> can contain:
  <ul>
    <li>
      An <code>Object</code> containing a single item to be
      added. The item must contain an id.
    </li>
    <li>
      An <code>Array</code> containing a list with items to be added. Each item must contain an id.
    </li>
  </ul>

  <p>
    After the items are added to the DataSet, the DataSet will
    trigger an event <code>add</code>. When a <code>senderId</code>
    is provided, this id will be passed with the triggered
    event to all subscribers.
  </p>

  <p>
    The method will throw an Error when an item with the same id
    as any of the added items already exists.
  </p>

  <h3 id="Update">Update</h3>

  <p>
    Update a data item or an array with items.
  </p>

  Syntax:
  <pre class="prettyprint lang-js">var updatedIds = DataSet.update(data [, senderId])</pre>

  The argument <code>data</code> can contain:
  <ul>
    <li>
      An <code>Object</code> containing a single item to be
      updated. The item must contain an id.
    </li>
    <li>
      An <code>Array</code> containing a list with items to be updated. Each item must contain an id.
    </li>
  </ul>

  <p>
    The provided properties will be merged in the existing item.
    When an item does not exist, it will be created.
  </p>

  <p>
    After the items are updated, the DataSet will
    trigger an event <code>add</code> for the added items, and
    an event <code>update</code>. When a <code>senderId</code>
    is provided, this id will be passed with the triggered
    event to all subscribers.
  </p>

  <h3 id="Remove">Remove</h3>

  <p>
    Remove a data item or an array with items.
  </p>

  Syntax:
  <pre class="prettyprint lang-js">var removedIds = DataSet.remove(id [, senderId])</pre>

  <p>
    The argument <code>id</code> can be:
  </p>
  <ul>
    <li>
      A <code>Number</code> or <code>String</code> containing the id
      of a single item to be removed.
    </li>
    <li>
      An <code>Object</code> containing the item to be deleted.
      The item will be deleted by its id.
    </li>
    <li>
      An Array containing ids or items to be removed.
    </li>
  </ul>

  <p>
    The method ignores removal of non-existing items, and returns an array
    containing the ids of the items which are actually removed from the
    DataSet.
  </p>

  <p>
    After the items are removed, the DataSet will
    trigger an event <code>remove</code> for the removed items.
    When a <code>senderId</code> is provided, this id will be passed with
    the triggered event to all subscribers.
  </p>


  <h3 id="Clear">Clear</h3>

  <p>
    Clear the complete DataSet.
  </p>

  Syntax:
  <pre class="prettyprint lang-js">var removedIds = DataSet.clear([senderId])</pre>

  <p>
    After the items are removed, the DataSet will
    trigger an event <code>remove</code> for all removed items.
    When a <code>senderId</code> is provided, this id will be passed with
    the triggered event to all subscribers.
  </p>


  <h2 id="Data_Selection">Data Selection</h2>

  <p>
    The DataSet contains functionality to format, filter, and sort data retrieved via the
    methods <code>get</code>, <code>getIds</code>, <code>forEach</code>, and <code>map</code>. These methods have the following syntax:
  </p>

<pre class="prettyprint lang-js">
DataSet.get([id] [, options]);
DataSet.getIds([options]);
DataSet.forEach(callback [, options]);
DataSet.map(callback [, options]);
</pre>

  <p>
    Where <code>options</code> is an Object which can have the following
    properties:
  </p>

  <table class="properties">
    <tr>
      <th>Name</th>
      <th>Type</th>
      <th>Required</th>
      <th>Description</th>
    </tr>

    <tr>
      <td>fields</td>
      <td>String[&nbsp;] | Object.&lt;String,&nbsp;String&gt;</td>
      <td>no</td>
      <td>
        An array with field names, or an object with current field name and
        new field name that the field is returned as.
        By default, all properties of the items are emitted.
        When <code>fields</code> is defined, only the properties
        whose name is specified in <code>fields</code> will be included
        in the returned items.
      </td>
    </tr>

    <tr>
      <td>type</td>
      <td>Object.&lt;String,&nbsp;String&gt;</td>
      <td>no</td>
      <td>
        An object containing field names as key, and data types as value.
        By default, the type of the properties of an item are left
        unchanged. When a field type is specified, this field in the
        items will be converted to the specified type. This can be used
        for example to convert ISO strings containing a date to a
        JavaScript Date object, or convert strings to numbers or vice
        versa. The available data types are listed in section
        <a href="#Data_Types">Data Types</a>.
      </td>
    </tr>

    <tr>
      <td>filter</td>
      <td>Function</td>
      <td>no</td>
      <td>Items can be filtered on specific properties by providing a filter
        function. A filter function is executed for each of the items in the
        DataSet, and is called with the item as parameter. The function must
        return a boolean. All items for which the filter function returns
        true will be emitted.
        See section <a href="#Data_Filtering">Data Filtering</a>.</td>
    </tr>

    <tr>
      <td>order</td>
      <td>String | Function</td>
      <td>no</td>
      <td>Order the items by a field name or custom sort function.</td>
    </tr>

    <tr>
      <td>returnType</td>
      <td>String</td>
      <td>no</td>
      <td>Determine the type of output of the get function. Allowed values are <code>'Array' | 'Object'</code>.
        The default returnType is an Array. The Object type will return a JSON object with the ID's as keys.</td>
    </tr>

  </table>

  <p>
    The following example demonstrates formatting properties and filtering
    properties from items.
  </p>

<pre class="prettyprint lang-js">
// create a DataSet
var data = new vis.DataSet();
data.add([
  {id: 1, text: 'item 1', date: '2013-06-20', group: 1, first: true},
  {id: 2, text: 'item 2', date: '2013-06-23', group: 2},
  {id: 3, text: 'item 3', date: '2013-06-25', group: 2},
  {id: 4, text: 'item 4'}
]);

// retrieve formatted items
var items = data.get({
  fields: ['id', 'date', 'group'],    // output the specified fields only
  type: {
    date: 'Date',                   // convert the date fields to Date objects
    group: 'String'                 // convert the group fields to Strings
  }
});
</pre>

  <h3 id="Getting_Data">Getting Data</h3>

  <p>
    Data can be retrieved from the DataSet using the method <code>get</code>.
    This method can return a single item or a list with items.
  </p>

  <p>A single item can be retrieved by its id:</p>

<pre class="prettyprint lang-js">
var item1 = dataset.get(1);
</pre>

  <p>A selection of items can be retrieved by providing an array with ids:</p>

<pre class="prettyprint lang-js">
var items = dataset.get([1, 3, 4]); // retrieve items 1, 3, and 4
</pre>

  <p>All items can be retrieved by simply calling <code>get</code> without
    specifying an id:</p>

<pre class="prettyprint lang-js">
var items = dataset.get();          // retrieve all items
</pre>


  <h3 id="Data_Filtering">Data Filtering</h3>

  <p>
    Items can be filtered on specific properties by providing a filter
    function. A filter function is executed for each of the items in the
    DataSet, and is called with the item as parameter. The function must
    return a boolean. All items for which the filter function returns
    true will be emitted.
  </p>

<pre class="prettyprint lang-js">
// retrieve all items having a property group with value 2
var group2 = dataset.get({
  filter: function (item) {
    return (item.group == 2);
  }
});

// retrieve all items having a property balance with a value above zero
var positiveBalance = dataset.get({
  filter: function (item) {
    return (item.balance > 0);
  }
});

</pre>


  <h3 id="Data_Types">Data Types</h3>

  <p>
    DataSet supports the following data types:
  </p>

  <table class="datatypes">
    <tr>
      <th>Name</th>
      <th>Description</th>
      <th>Examples</th>
    </tr>
    <tr>
      <td>Boolean</td>
      <td>A JavaScript Boolean</td>
      <td>
        <code>true</code><br>
        <code>false</code>
      </td>
    </tr>
    <tr>
      <td>Number</td>
      <td>A JavaScript Number</td>
      <td>
        <code>32</code><br>
        <code>2.4</code>
      </td>
    </tr>
    <tr>
      <td>String</td>
      <td>A JavaScript String</td>
      <td>
        <code>"hello world"</code><br>
        <code>"2013-06-28"</code>
      </td>
    </tr>
    <tr>
      <td>Date</td>
      <td>A JavaScript Date object</td>
      <td>
        <code>new Date()</code><br>
        <code>new Date(2013, 5, 28)</code><br>
        <code>new Date(1372370400000)</code>
      </td>
    </tr>
    <tr>
      <td>Moment</td>
      <td>A Moment object, created with
        <a href="http://momentjs.com/" target="_blank">moment.js</a></td>
      <td>
        <code>moment()</code><br>
        <code>moment('2013-06-28')</code>
      </td>
    </tr>
    <tr>
      <td>ISODate</td>
      <td>A string containing an ISO Date</td>
      <td>
        <code>new Date().toISOString()</code><br>
        <code>"2013-06-27T22:00:00.000Z"</code>
      </td>
    </tr>
    <tr>
      <td>ASPDate</td>
      <td>A string containing an ASP Date</td>
      <td>
        <code>"/Date(1372370400000)/"</code><br>
        <code>"/Date(1198908717056-0700)/"</code>
      </td>
    </tr>
  </table>

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