0_graph.ascii

          +------------------+
          |  what are your   |
          | favourite foods? |
          +------------------+   
            |              |
    +--------+            +-----------+
    | Fruit  |            | Vegetable |
    +--------+            +-----------+
      |     |                  |
+-------+   +--------+     +----------+
| Apple |   | Banana |     | Broccoli |
+-------+   +--------+     +----------+

1

// 1. separate category nodes

{
  nodes: {
    chk1: {
      $t: TYPES.Checklist,
      text: "What are your favourite foods?"
    },
    cat1: {
      $t: TYPES.ChecklistCategory,
      text: "Fruit"
    },
    cat2: {
      $t: TYPES.ChecklistCategory,
      text: "Vegetable"
    },
    res1: {
      $t: TYPES.Response,
      text: "Apple"
    },
    res2: {
      $t: TYPES.Response,
      text: "Banana"
    },
    res3: {
      $t: TYPES.Response,
      text: "Broccoli"
    }
  },
  edges: [
    [null, chk1],
    [chk1, cat1],
    [chk1, cat2],
    [cat1, res1],
    [cat1, res2],
    [cat2, res3],
  ]
}

2

// 2. store category values inside responses

{
  nodes: {
    chk1: {
      $t: TYPES.Checklist,
      text: "What are your favourite foods?"
    },
    res1: {
      $t: TYPES.Response,
      text: "Apple",
      category: "Fruit"
    },
    res2: {
      $t: TYPES.Response,
      text: "Banana",
      category: "Fruit"
    },
    res3: {
      $t: TYPES.Response,
      text: "Broccoli",
      category: "Vegetable"
    }
  },
  edges: [
    [null, chk1],
    [chk1, res1],
    [chk1, res2],
    [chk1, res3],
  ]
}

3

// 3. store category index inside responses

{
  nodes: {
    chk1: {
      $t: TYPES.Checklist,
      text: "What are your favourite foods?",
      categories: ["Fruit", "Vegetable"]
    },
    res1: {
      $t: TYPES.Response,
      text: "Apple",
      category: 0
    },
    res2: {
      $t: TYPES.Response,
      text: "Banana",
      category: 0
    },
    res3: {
      $t: TYPES.Response,
      text: "Broccoli",
      category: 1
    }
  },
  edges: [
    [null, chk1],
    [chk1, res1],
    [chk1, res2],
    [chk1, res3],
  ]
}

4

// 4. Store categories and the count/number of responses they apply to 
//    in an object (keys have guaranteed order so it can be iterated)
//    there are 2 fruits and 1 vegetable, so Fruit=2, Vegetable=1

{
  nodes: {
    chk1: {
      $t: TYPES.Checklist,
      text: "What are your favourite foods?",
      categories: {
        "Fruit": 2,
        "Vegetable": 1,
      }
    },
    res1: {
      $t: TYPES.Response,
      text: "Apple"
    },
    res2: {
      $t: TYPES.Response,
      text: "Banana"
    },
    res3: {
      $t: TYPES.Response,
      text: "Broccoli"
    }
  },
  edges: [
    [null, chk1],
    [chk1, res1],
    [chk1, res2],
    [chk1, res3],
  ]
}