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Add a Timeline to Your Website with Google Charts

Ashraff Hathibelagal
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To grab a reader’s attention, it is a good idea to display your datasets in the form of charts instead of tables. If you are talking about a lot of events on your blog, displaying those events in a chronological order on a timeline will communicate the message in a more effective and interesting manner.

In this tutorial, I’ll teach you how to use Google Charts to add professional looking timelines to your web pages.

Loading Google Charts

Since I’m going to make use of Google API Loader to load Google Charts, I’ll add the following script tag to the header of the page that’s going to display the timeline:

<script type="text/javascript" src="https://www.google.com/jsapi"></script>

I can now use the google.load method to load any Google API. For Google Charts, I’ll need to load the Visualization API along with the timeline package of the API. I’ll also add a callback to know when the API is ready.

google.load('visualization', '1.0', { packages:["timeline"] });
google.setOnLoadCallback(start);

function start() {
  /* This method will be called when the
     Visualization API has been loaded. */
}

Adding an Element to Hold the Chart

The Charts API needs an HTML element to draw its charts. I’ll add an empty div to the body of the page and call it timelineHolder. I can set the dimensions of your timeline by setting the width and height properties of in the CSS. Let’s create a timeline with dimensions of 600px x 300px.

.timelineHolder {
  width: 600px;
  height: 300px;
}

Defining the Timeline’s Data

For this tutorial, let us represent a year in the life of an imaginary traveler, named Alice, on a timeline. Here’s what Alice did that year:

  • From January 15 to February 26 she was in Berlin
  • From April 20 to July 1 she was in Paris
  • From July 21 to August 30 she was in Madrid
  • From November 2 to December 5 she was in Perth

This information has to be converted into a DataTable. Our DataTable is going to have four columns:

  • Label
  • Place
  • Start Date
  • End Date

Create a new function called prepareDataTable() to create and initialize the DataTable. We have to use the addColumn method to add each of the four columns. Once the columns have been added, use the addRow method to add all the four trips. Remember, dates have to be represented as Date objects and months are numbered 0-11 (instead of 1-12). Here’s how our function should look:

function prepareDataTable() {
  var dataTable = new google.visualization.DataTable();

  // Add columns
  dataTable.addColumn({ type: 'string', id: 'Label'});
  dataTable.addColumn({ type: 'string', id: 'Place'});
  dataTable.addColumn({ type: 'date', id: 'Arrival Date'});
  dataTable.addColumn({ type: 'date', id: 'Departure Date'});

  //Add Rows
  dataTable.addRow(['1', 'Berlin',
                    new Date(2014, 0, 15), new Date(2014, 1, 26)]);
  dataTable.addRow(['2', 'Paris', 
                    new Date(2014, 3, 20), new Date(2014, 6, 1)]);
  dataTable.addRow(['3', 'Madrid', 
                    new Date(2014, 6, 21), new Date(2014, 7, 30)]);
  dataTable.addRow(['4', 'Perth', 
                    new Date(2014, 10, 2), new Date(2014, 11, 5)]);

  return dataTable;
}

Take note that the first column of the DataTable is always treated as a label of a row by the Charts API.

Drawing the Timeline

Now that the data has been converted into a format that the Google Charts API understands, we can draw the timeline. To do this, we’ll create an instance of the Timeline class, and then pass the DataTable to its draw method. We’ll update the start method to do so:

function start() {
  // Pick the HTML element
  var timelineHolder = document.getElementById("timelineHolder");

  // Create an instance of Timeline
  var timeline = new google.visualization.Timeline(timelineHolder);
  var dataTable = prepareDataTable();

  // Draw the timeline
  timeline.draw(dataTable);
}

At this point, if you load your page using a browser, you will see a timeline that looks like this:

See the Pen b0522e3f0762ae90ce00c0f92438e8aa by SitePoint (@SitePoint) on CodePen.

Customizing the Timeline

Changing the appearance of the timeline involves creating a JSON object that contains one or more names of properties along with your preferred values for those properties.

For example, if we wish to change the background color of the timeline to #ffbb33 and use a single color for all the trips, say #669900, we will have to create the following JSON object:

var config = {
  backgroundColor: '#ffbb33',
  timeline: { singleColor: '#669900' }
}

We then pass this object as an additional parameter to the timeline’s draw method:

timeline.draw(dataTable, config);

On refreshing our page in the browser, our timeline will look like this:

See the Pen Google Charts Demo: Custom Colors by SitePoint (@SitePoint) on CodePen.

For a complete list of all available configuration options, refer to the Google Charts timeline documentation.

You may have noticed that the trips are placed one below the other, with each on its own line/row. This is because we used a different row label for each row. To place all trips on a single line, you will have to change the first column of your DataTable such that all the four entries have the same row label.

For our example, we’ll use Alice’s Travels as the label for all the rows. We’ll update our prepareDataTable function so that the addRow calls look like this:

dataTable.addRow(['Alice\'s Travels', 'Berlin', new Date(2014, 0, 15), 
                   new Date(2014, 1, 26)]);
dataTable.addRow(['Alice\'s Travels', 'Paris', new Date(2014, 3, 20), 
                   new Date(2014, 6, 1)]);
dataTable.addRow(['Alice\'s Travels', 'Madrid', new Date(2014, 6, 21), 
                   new Date(2014, 7, 30)]);
dataTable.addRow(['Alice\'s Travels', 'Perth', new Date(2014, 10, 2), 
                   new Date(2014, 11, 5)]);

The timeline will now look more compact:

See the Pen Google Charts Demo: Compact Timeline by SitePoint (@SitePoint) on CodePen.

Adding Interactivity

Our timeline is already interactive. Hovering over any trip displays a tooltip with some autogenerated content.

To add a custom behavior when a data item is clicked on, we have to add a handler for the select event using the google.visualization.events.addListener method. In the handler, we can use the getSelection method to determine which item was clicked.

Here’s a sample handler that displays the currently selected place. You can add it at the end of the start function, after calling the draw method:

google.visualization.events.addListener(timeline, 'select', function() {
  alert(dataTable.getValue(getSelection()[0].row, 1);
});

See the Pen Google Charts Demo: Showing an Alert Message by SitePoint (@SitePoint) on CodePen.

Conclusion

In this tutorial, I showed you how to use Google Charts to display events in a chronological order on a timeline chart that can easily be added to any web page. I also showed you how to customize the chart and make it interactive. To learn more about the timeline chart, refer to the Timeline Documentation.