Conditional styling for cytoscape

Question

I want to add conditional styles for cytoscape elements (nodes and edges). I read conditional styles for cytoscape but this seems to add style conditionals after the graph is rendered which I think is not very good when there are a lot of conditions.

        style: {
            "content": "data(label)",
            "shape": "round-rectangle",
            "width": "150px",
            "text-valign": "center",
            "background-color": "data(error)" ? "red" : "green"
        }

I want to set background based on the value of error property. This does not work as "data(error)" is a string. I tried "data(error)" === "true" but that also did not work. Can you please help me out?

Answer 1

You can use a simple function block to achieve this. The function has one parameter, which is the current node. You can access the node by calling the .data(attr) method:

document.addEventListener("DOMContentLoaded", function() {
  var cy = (window.cy = cytoscape({
    container: document.getElementById("cy"),

    layout: {
      name: "klay"
    },

    style: [{
        selector: "node",
        style: {
          // You can use function(node){} instead of ES6 syntax here
          "background-color": node => node.data('error') ? 'red' : 'green',
          "content": "data(label)",
          "shape": "round-rectangle",
          "width": "50px",
          "text-valign": "center"
        }
      },
      {
        selector: "edge",
        style: {
          "curve-style": "bezier",
          "target-arrow-shape": "triangle",
          "line-color": "#dd4de2",
          "target-arrow-color": "#dd4de2",
          opacity: 0.5
        }
      }
    ],
    elements: {
      nodes: [{
          data: {
            id: "n0",
            label: "n0",
            error: true
          }
        },
        {
          data: {
            id: "n1",
            label: "n1",
            error: false
          }
        },
        {
          data: {
            id: "n2",
            label: "n2",
            error: false
          }
        },
        {
          data: {
            id: "n3",
            label: "n3",
            error: false
          }
        },
        {
          data: {
            id: "n4",
            label: "n4",
            error: true
          }
        },
        {
          data: {
            id: "n5",
            label: "n5",
            error: true
          }
        },
        {
          data: {
            id: "n6",
            label: "n6",
            error: false
          }
        },
        {
          data: {
            id: "n7",
            label: "n7",
            error: false
          }
        },
        {
          data: {
            id: "n8",
            label: "n8",
            error: false
          }
        },
        {
          data: {
            id: "n9",
            label: "n9",
            error: true
          }
        },
        {
          data: {
            id: "n10",
            label: "n10",
            error: true
          }
        },
        {
          data: {
            id: "n11",
            label: "n11",
            error: false
          }
        },
        {
          data: {
            id: "n12",
            label: "n12",
            error: true
          }
        },
        {
          data: {
            id: "n13",
            label: "n13",
            error: false
          }
        },
        {
          data: {
            id: "n14",
            label: "n14",
            error: true
          }
        },
        {
          data: {
            id: "n15",
            label: "n15",
            error: false
          }
        }
      ],
      edges: [{
          data: {
            source: "n0",
            target: "n1"
          }
        },
        {
          data: {
            source: "n1",
            target: "n2"
          }
        },
        {
          data: {
            source: "n1",
            target: "n3"
          }
        },
        {
          data: {
            source: "n2",
            target: "n4"
          }
        },
        {
          data: {
            source: "n4",
            target: "n5"
          }
        },
        {
          data: {
            source: "n4",
            target: "n6"
          }
        },
        {
          data: {
            source: "n6",
            target: "n7"
          }
        },
        {
          data: {
            source: "n6",
            target: "n8"
          }
        },
        {
          data: {
            source: "n8",
            target: "n9"
          }
        },
        {
          data: {
            source: "n8",
            target: "n10"
          }
        },
        {
          data: {
            source: "n10",
            target: "n11"
          }
        },
        {
          data: {
            source: "n11",
            target: "n12"
          }
        },
        {
          data: {
            source: "n12",
            target: "n13"
          }
        },
        {
          data: {
            source: "n13",
            target: "n14"
          }
        },
        {
          data: {
            source: "n13",
            target: "n15"
          }
        }
      ]
    }
  }));
});

body {
  font-family: helvetica neue, helvetica, liberation sans, arial, sans-serif;
  font-size: 14px;
}

#cy {
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  right: 0;
  z-index: 999;
}

<html>

<head>
  <script src="https://unpkg.com/cytoscape/dist/cytoscape.min.js"></script>
  <script src="https://unpkg.com/klayjs@0.4.1/klay.js"></script>
  <script src="https://cdn.jsdelivr.net/npm/cytoscape-klay@3.1.3/cytoscape-klay.min.js"></script>
</head>

<body>
  <div id="cy"></div>
</body>

</html>

I would generally suggest to use classes instead of conditional css though:

document.addEventListener("DOMContentLoaded", function() {
  var cy = (window.cy = cytoscape({
    container: document.getElementById("cy"),

    layout: {
      name: "klay"
    },

    style: [{
        selector: "node",
        style: {
          "background-color": 'green',
          "content": "data(label)",
          "shape": "round-rectangle",
          "width": "50px",
          "text-valign": "center"
        }
      },
      {
        selector: ".danger",
        style: {
          "background-color": 'red'
        }
      },
      
      {
        selector: "edge",
        style: {
          "curve-style": "bezier",
          "target-arrow-shape": "triangle",
          "line-color": "#dd4de2",
          "target-arrow-color": "#dd4de2",
          opacity: 0.5
        }
      }
    ],
    elements: {
      nodes: [{
          data: {
            id: "n0",
            label: "n0",
            error: true
          },
          classes: 'danger'
        },
        {
          data: {
            id: "n1",
            label: "n1",
            error: false
          }
        },
        {
          data: {
            id: "n2",
            label: "n2",
            error: false
          }
        },
        {
          data: {
            id: "n3",
            label: "n3",
            error: false
          }
        },
        {
          data: {
            id: "n4",
            label: "n4",
            error: true
          }
        },
        {
          data: {
            id: "n5",
            label: "n5",
            error: true
          },
          classes: 'danger'
        },
        {
          data: {
            id: "n6",
            label: "n6",
            error: false
          }
        },
        {
          data: {
            id: "n7",
            label: "n7",
            error: false
          }
        },
        {
          data: {
            id: "n8",
            label: "n8",
            error: false
          }
        },
        {
          data: {
            id: "n9",
            label: "n9",
            error: true
          }
        },
        {
          data: {
            id: "n10",
            label: "n10",
            error: true
          }
        },
        {
          data: {
            id: "n11",
            label: "n11",
            error: false
          }
        },
        {
          data: {
            id: "n12",
            label: "n12",
            error: true
          }
        },
        {
          data: {
            id: "n13",
            label: "n13",
            error: false
          }
        },
        {
          data: {
            id: "n14",
            label: "n14",
            error: true
          }
        },
        {
          data: {
            id: "n15",
            label: "n15",
            error: false
          }
        }
      ],
      edges: [{
          data: {
            source: "n0",
            target: "n1"
          }
        },
        {
          data: {
            source: "n1",
            target: "n2"
          }
        },
        {
          data: {
            source: "n1",
            target: "n3"
          }
        },
        {
          data: {
            source: "n2",
            target: "n4"
          }
        },
        {
          data: {
            source: "n4",
            target: "n5"
          }
        },
        {
          data: {
            source: "n4",
            target: "n6"
          }
        },
        {
          data: {
            source: "n6",
            target: "n7"
          }
        },
        {
          data: {
            source: "n6",
            target: "n8"
          }
        },
        {
          data: {
            source: "n8",
            target: "n9"
          }
        },
        {
          data: {
            source: "n8",
            target: "n10"
          }
        },
        {
          data: {
            source: "n10",
            target: "n11"
          }
        },
        {
          data: {
            source: "n11",
            target: "n12"
          }
        },
        {
          data: {
            source: "n12",
            target: "n13"
          }
        },
        {
          data: {
            source: "n13",
            target: "n14"
          }
        },
        {
          data: {
            source: "n13",
            target: "n15"
          }
        }
      ]
    }
  }));
});

body {
  font-family: helvetica neue, helvetica, liberation sans, arial, sans-serif;
  font-size: 14px;
}

#cy {
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  right: 0;
  z-index: 999;
}

<html>

<head>
  <script src="https://unpkg.com/cytoscape/dist/cytoscape.min.js"></script>
  <script src="https://unpkg.com/klayjs@0.4.1/klay.js"></script>
  <script src="https://cdn.jsdelivr.net/npm/cytoscape-klay@3.1.3/cytoscape-klay.min.js"></script>
</head>

<body>
  <div id="cy"></div>
</body>

</html>