How connect multiple numbers in a array of objects-CodePudding

I've been trying to find the solution for a few days but no success. It is only exemple I need of a function that execute this with any selectedNode. I will use it in a graph.

The array:

const edges = [
        {
            "id": "e1-2",
            "from": "1",
            "to": "2"
        },
        {
            "id": "e2-3",
            "from": "2",
            "to": "3"
        },
        {
            "id": "e2-8",
            "from": "2",
            "to": "8"
        },
        {
            "id": "e2-13",
            "from": "2",
            "to": "13"
        },
        {
            "id": "e3-4",
            "from": "3",
            "to": "4"
        },
        {
            "id": "e4-5",
            "from": "4",
            "to": "5"
        },
        {
            "id": "e4-6",
            "from": "4",
            "to": "6"
        },
        {
            "id": "e4-7",
            "from": "4",
            "to": "7"
        },
        {
            "id": "e8-9",
            "from": "8",
            "to": "9"
        },
        {
            "id": "e9-10",
            "from": "9",
            "to": "10"
        },
        {
            "id": "e9-11",
            "from": "9",
            "to": "11"
        },
        {
            "id": "e9-12",
            "from": "9",
            "to": "12"
        },
        {
            "id": "e13-14",
            "from": "13",
            "to": "14"
        },
        {
            "id": "e14-15",
            "from": "14",
            "to": "15"
        },
        {
            "id": "e14-16",
            "from": "14",
            "to": "16"
        },
        {
            "id": "e14-17",
            "from": "14",
            "to": "17"
        },
        {
            "id": "e14-18",
            "from": "14",
            "to": "18"
        },
        {
            "id": "e14-19",
            "from": "14",
            "to": "19"
        }
    ]

I trying use filter and map but only catch the first children. I need the children of children and so on.

const selectedNode = "2";

const connections = edges
      .filter((edge) => edge.from === selectedNode).map((edge) => edge.to)




console.log(connections)

The output:

[LOG]: ["3", "8", "13"]

but i need all children as cascade.

Like this output:

["3", "8", "13", "4", "5", "6", "7", "9", "10", "11", "12", "14", "15", "16", "17", "18", "19"]

But if the selectedNode was "8", the array would be:

["9", "10", "11", "12"]

CodePudding user response：

You need to make a recursive algorithm of some kind. One approach would be to restructure the edges into a mapping by froms first. Then, when iterating over an edge (starting with the selectedNode), if the edge's to contains any other tos, perform the recursive call for each one.

const edges=[{id:"e1-2",from:"1",to:"2"},{id:"e2-3",from:"2",to:"3"},{id:"e2-8",from:"2",to:"8"},{id:"e2-13",from:"2",to:"13"},{id:"e3-4",from:"3",to:"4"},{id:"e4-5",from:"4",to:"5"},{id:"e4-6",from:"4",to:"6"},{id:"e4-7",from:"4",to:"7"},{id:"e8-9",from:"8",to:"9"},{id:"e9-10",from:"9",to:"10"},{id:"e9-11",from:"9",to:"11"},{id:"e9-12",from:"9",to:"12"},{id:"e13-14",from:"13",to:"14"},{id:"e14-15",from:"14",to:"15"},{id:"e14-16",from:"14",to:"16"},{id:"e14-17",from:"14",to:"17"},{id:"e14-18",from:"14",to:"18"},{id:"e14-19",from:"14",to:"19"}];

const toByFrom = {};
for (const edge of edges) {
  toByFrom[edge.from] ??= [];
  toByFrom[edge.from].push(edge.to);
}
const allNodes = [];
const getNodes = (parent, allNodes = []) => {
  const tos = toByFrom[parent];
  if (tos) {
    allNodes.push(...tos);
    for (const to of tos) {
      getNodes(to, allNodes);
    }
  }
  return allNodes;
};
console.log(getNodes('2'));

CodePudding user response：

This sounds like a recursion mission. This is the same answer as the other one. Only as a function.

const edges = [{ "id": "e1-2", "from": "1", "to": "2" }, { "id": "e2-3", "from": "2", "to": "3" }, { "id": "e2-8", "from": "2", "to": "8" }, { "id": "e2-13", "from": "2", "to": "13" }, { "id": "e3-4", "from": "3", "to": "4" }, { "id": "e4-5", "from": "4", "to": "5" }, { "id": "e4-6", "from": "4", "to": "6" }, { "id": "e4-7", "from": "4", "to": "7" }, { "id": "e8-9", "from": "8", "to": "9" }, { "id": "e9-10", "from": "9", "to": "10" }, { "id": "e9-11", "from": "9", "to": "11" }, { "id": "e9-12", "from": "9", "to": "12" }, { "id": "e13-14", "from": "13", "to": "14" }, { "id": "e14-15", "from": "14", "to": "15" }, { "id": "e14-16", "from": "14", "to": "16" }, { "id": "e14-17", "from": "14", "to": "17" }, { "id": "e14-18", "from": "14", "to": "18" }, { "id": "e14-19", "from": "14", "to": "19" }];

function find_immediate_edges(selected) {
  return edges.filter(item => item.from == selected).map(item => item.to);
}

function find_edges(selected) {
  var result = []
  
  function loop(selected) {
    var immediate = find_immediate_edges(selected);
    result = result.concat(immediate)
    immediate.forEach(loop)
  }
  
  loop(selected);
  return result;
}


console.log(""   find_edges(2));
console.log(""   find_edges(8));