Is it possible to color just one node of the graph in CytoscapeJS?

Question

Can I select a specific node and color it with a different color of the rest of the graph?

Thanks.

Answer 1

There are many ways to do it. You can change the color of a node by its ID using cy.nodes([id="NODE_ID"]) and set any style you want (more info).

If what you need is to change the color of a node when it is selected (clicked on) you can use cy.on('tap', ...) in a similar way (more info).

Here is a small demo of both:

var eleArray = [
  { group: 'nodes', data: { id: 'N1'} },
  { group: 'nodes', data: { id: 'N2'} },
  { group: 'nodes', data: { id: 'N3'} },
  { group: 'edges', data: { id: 'E0', source: 'N1', target: 'N2' } },
  { group: 'edges', data: { id: 'E1', source: 'N2', target: 'N3' } }
];

var stylesArray = [{
  selector: 'node',
  style: {'label': 'data(id)'}
}];

var cy = cytoscape({
  container: document.getElementById('cy'),
  style: stylesArray,
  elements: eleArray
});

// Set color of a node by ID
cy.nodes('[id="N2"]').style('background-color', 'red');

// Set color of a node when clicked
cy.on('tap', 'node', function(evt) {
  evt.target.style({
    'background-color': 'blue'
  });
});

#cy {
  width: 90%;
  height: 200px;
  display: block;
}

<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/cytoscape/3.14.1/cytoscape.min.js"></script>
<div id="cy"></div>

Notice how I changed the color of the node N2 to red directly, and how the color changes to blue when you click on a node.

If your graph is very complex, maybe a better way would be to add the color as a property of your nodes and using that property data on your style definition. Something like this:

// New 'color' property on your nodes
var eleArray = [
   { group: 'nodes', data: { id: 'N1', color: 'red'} }
   // ...
];

// Use the property on your styles
var stylesArray = [{
   selector: 'node',
   style: {'label': 'data(id)', 'background-color': 'data(color)'}
}];