getEdgeData array[connId] is undefined

[kowdykung]

I am working on saveAndLoad and manipulation example

I got this network which load form JSON.

I deleted node 1 and its edge, then I export to JSON file. I got the correct JSON file.

[
  {
    "x": 0,
    "y": -1,
    "id": "0",
    "connections": [
      "3",
      "2"
    ]
  },
  {
    "x": 123,
    "y": -7,
    "id": "2",
    "connections": [
      "0"
    ]
  },
  {
    "x": -52,
    "y": -115,
    "id": "3",
    "connections": [
      "0"
    ]
  }
]

When I want to load this JSON back but it's got an error on import JSON in function getEdgeData

I don't know why this function error as I see it should be correct because of JSON is correct.

var ourRequest = new XMLHttpRequest();
			ourRequest.open('GET','http://localhost/2.json');
			var inputData;
			ourRequest.onload = function() {
				inputData = JSON.parse(ourRequest.responseText);
				nodes = getNodeData(inputData);
				edges = getEdgeData(inputData);
				data = {
						nodes: nodes,
						edges: edges
				};

			};
			ourRequest.send();

[wimrijnders]

Reproducing this with saveAndLoad example in chromium/linux, I get the error:

Uncaught TypeError: Cannot read property 'connections' of undefined
    at file:///home/wim/projects/github/issues/%232938/saveAndLoad.html:158:63
    ...

I believe this is the same error as reported with a different text. Location in code, in saveAndLoad.html:

function getEdgeData(data) {
  var networkEdges = [];

  data.forEach(function(node, index, array) {
  // add the connection
    node.connections.forEach(function(connId, cIndex, conns) {
      networkEdges.push({from: node.id, to: connId});

      var elementConnections = array[connId].connections;   // <= ERROR HAPPENS HERE
...

    });
  });

  return new vis.DataSet(networkEdges);
}

[wimrijnders]

What I notice, is that on export, the node id's get renumbered. When I delete node 1, the following is exported:

[
  {
    "x": 1,
    "y": 0,
    "id": 0,
    "connections": [
      2,
      3
    ]
  },
  {
    "x": -7,
    "y": -123,
    "id": 1,
    "connections": []
  },
  {
    "x": 95,
    "y": 83,
    "id": 2,
    "connections": [
      0
    ]
  }
]

I note that id: 3 is missing in the node id's, but that it does feature in the connections.

@kowdykung, are you sure that your example JSON file is as how it was exported?

In any case, this is the problem; the node id's are renumbered on export, but the id's in the connections aren't. The source of the problem can be traced to the following two items:

1. Only position information is used on export:

function exportNetwork() {
	clearOutputArea();

	var nodes = objectToArray(network.getPositions());
...
}

2. The node index is used to set the exported node id's:

function addId(elem, index) {
  elem.id = index;
}

I conclude that issue is in the saveAndLoad demo. I'll think now how to solve this.

[wimrijnders]

I figured it out. This will require a PR to fix fully.

For your personal case, assuming you're using code from the saveAndLoad example, please make the following changes:

             function addContextualInformation(elem, index, array) {
                //addId(elem, index);                    // CHANGED
                 addConnections(elem, index);
             }

            // NEW 
            function getNodeById(data, id) {
              var foundNode;

              data.forEach(function(node) {
                if (node.id == id) {  // double equals since id can be numeric or string
                  foundNode = node;
                }
              });

              if (foundNode === undefined) {
                throw 'Can not find id \'' + id + '\' in data';
              }

              return foundNode;
            }


             // CHANGED - please copy this over the existing function
             function getEdgeData(data) {
                 var networkEdges = [];
 
                     // add the connection
                     node.connections.forEach(function(connId, cIndex, conns) {
                         networkEdges.push({from: node.id, to: connId});
                        let cNode = getNodeById(data, connId);
 
                        var elementConnections = cNode.connections;
 
                         // remove the connection from the other node to prevent duplicate connections
                         var duplicateIndex = elementConnections.findIndex(function(connection) {
                          return connection == node.id; // double equals since id can be numeric or string
                         });

                        if (duplicateIndex != -1) {
                          elementConnections.splice(duplicateIndex, 1);
                        };
                  });
                 });
 
                 return new vis.DataSet(networkEdges);
             }

             // CHANGED - please copy this over the existing function
             function objectToArray(obj) {
                return Object.keys(obj).map(function (key) {
                  obj[key].id = key;
                  return obj[key];
                });
             }

(I'm truly sorry that I can not make it simpler than this)