将最大值传播到嵌套树javascript中的父节点

Question

Having a nested array like the following one:

[
    {
        "id": 100,
        "idParent": null,
        "anidatedView": null,
        "state": null,
        "warningHighThreshold": null,
        "dangerHighThreshold": null,
        "lvl": 1,
        "children": [
            {
                "id": 139,
                "idParent": 100,
                "anidatedView": null,
                "state": null,
                "warningHighThreshold": null,
                "dangerHighThreshold": null,
                "lvl": 2,
                "children": [
                    {
                        "id": 186,
                        "idParent": 139,
                        "anidatedView": 279,
                        "state": 15.58,
                        "warningHighThreshold": 80,
                        "dangerHighThreshold": 100,
                        "lvl": 3,
                        "children": []
                    },
                    {
                        "id": 189,
                        "idParent": 139,
                        "anidatedView": 193,
                        "state": 40.65,
                        "warningHighThreshold": 80,
                        "dangerHighThreshold": 100,
                        "lvl": 3,
                        "children": []
                    }
                ]
            },
            {
                "id": 140,
                "idParent": 100,
                "anidatedView": null,
                "state": null,
                "warningHighThreshold": null,
                "dangerHighThreshold": null,
                "lvl": 2,
                "children": [
                    {
                        "id": 193,
                        "idParent": 140,
                        "anidatedView": 183,
                        "state": 65.41,
                        "warningHighThreshold": 92,
                        "dangerHighThreshold": 100,
                        "lvl": 3,
                        "children": []
                    }
                ]
            },
            {
                "id": 141,
                "idParent": 100,
                "anidatedView": null,
                "state": null,
                "warningHighThreshold": null,
                "dangerHighThreshold": null,
                "lvl": 2,
                "children": [
                    {
                        "id": 194,
                        "idParent": 141,
                        "anidatedView": 143,
                        "state": 60.77,
                        "warningHighThreshold": 90,
                        "dangerHighThreshold": 100,
                        "lvl": 3,
                        "children": []
                    },
                    {
                        "id": 195,
                        "idParent": 141,
                        "anidatedView": 436,
                        "state": 59.13,
                        "warningHighThreshold": 90,
                        "dangerHighThreshold": 100,
                        "lvl": 3,
                        "children": []
                    }
                ]
            }
        ]
    }
]

I´m trying to propagate the max value of state(also warningHighThreshold and dangerHighThreshold of that max node) to all parent nodes.
State and thresholds values will be always avalable on the last level on the tree.

Any idea how to do this with recursion?

Thanks in advance!

Answer 1

I have finally managed to solve the problem. I leave my solution for those who may have the same issue.

const populateState = item => {
  if (item.children.length) {
    const maxValue = item.children
      .map(child => populateState(child))
      .filter(({ state }) => state != null)
      .reduce((maxValue, value) => (value.state > maxValue.state ? value : maxValue), { state: -1 })
    item.state = maxValue.state
    item.warningHighThreshold = maxValue.warningHighThreshold
    item.dangerHighThreshold = maxValue.dangerHighThreshold
    return maxValue
  } else {
    const { state, warningHighThreshold, dangerHighThreshold } = item
    return { state, warningHighThreshold, dangerHighThreshold }
  }
}

Usage:
(The array variable is the list I`ve defined in the question)

populateState({ children: array})

Any code enhancement is welcome.

Answer 2

Try this:

 const list = JSON.parse(`[ { "id": 100, "idParent": null, "anidatedView": null, "state": null, "warningHighThreshold": null, "dangerHighThreshold": null, "lvl": 1, "children": [ { "id": 139, "idParent": 100, "anidatedView": null, "state": null, "warningHighThreshold": null, "dangerHighThreshold": null, "lvl": 2, "children": [ { "id": 186, "idParent": 139, "anidatedView": 279, "state": 15.58, "warningHighThreshold": 80, "dangerHighThreshold": 100, "lvl": 3, "children": [] }, { "id": 189, "idParent": 139, "anidatedView": 193, "state": 40.65, "warningHighThreshold": 80, "dangerHighThreshold": 100, "lvl": 3, "children": [] } ] }, { "id": 140, "idParent": 100, "anidatedView": null, "state": null, "warningHighThreshold": null, "dangerHighThreshold": null, "lvl": 2, "children": [ { "id": 193, "idParent": 140, "anidatedView": 183, "state": 65.41, "warningHighThreshold": 92, "dangerHighThreshold": 100, "lvl": 3, "children": [] } ] }, { "id": 141, "idParent": 100, "anidatedView": null, "state": null, "warningHighThreshold": null, "dangerHighThreshold": null, "lvl": 2, "children": [ { "id": 194, "idParent": 141, "anidatedView": 143, "state": 60.77, "warningHighThreshold": 90, "dangerHighThreshold": 101, "lvl": 3, "children": [] }, { "id": 195, "idParent": 141, "anidatedView": 436, "state": 59.13, "warningHighThreshold": 90, "dangerHighThreshold": 100, "lvl": 3, "children": [] } ] } ] } ]`); function getHigh(obj, prop) { let ret = null; for(let n = 0; n < 2; n++) { for(let i = 0; i < obj.length; i++) { const r = getHigh(obj[i].children, prop); if (r > obj[i][prop]) { obj[i][prop] = r; ret = r; } if (obj[i][prop] > ret) ret = obj[i][prop]; } } return ret; } console.log("warningHighThreshold", getHigh(list, "warningHighThreshold")); console.log(JSON.stringify(list, null, 2)); console.log("dangerHighThreshold", getHigh(list, "dangerHighThreshold")); console.log(JSON.stringify(list, null, 2));

Answer 3

This kind of problem could be solve with depth first search...

 let input = [{ "id": 100, "idParent": null, "anidatedView": null, "state": null, "warningHighThreshold": null, "dangerHighThreshold": null, "lvl": 1, "children": [{ "id": 139, "idParent": 100, "anidatedView": null, "state": null, "warningHighThreshold": null, "dangerHighThreshold": null, "lvl": 2, "children": [{ "id": 186, "idParent": 139, "anidatedView": 279, "state": 15.58, "warningHighThreshold": 80, "dangerHighThreshold": 100, "lvl": 3, "children": [] }, { "id": 189, "idParent": 139, "anidatedView": 193, "state": 40.65, "warningHighThreshold": 80, "dangerHighThreshold": 100, "lvl": 3, "children": [] }] }, { "id": 140, "idParent": 100, "anidatedView": null, "state": null, "warningHighThreshold": null, "dangerHighThreshold": null, "lvl": 2, "children": [{ "id": 193, "idParent": 140, "anidatedView": 183, "state": 65.41, "warningHighThreshold": 92, "dangerHighThreshold": 100, "lvl": 3, "children": [] }] }, { "id": 141, "idParent": 100, "anidatedView": null, "state": null, "warningHighThreshold": null, "dangerHighThreshold": null, "lvl": 2, "children": [{ "id": 194, "idParent": 141, "anidatedView": 143, "state": 60.77, "warningHighThreshold": 90, "dangerHighThreshold": 100, "lvl": 3, "children": [] }, { "id": 195, "idParent": 141, "anidatedView": 436, "state": 59.13, "warningHighThreshold": 90, "dangerHighThreshold": 100, "lvl": 3, "children": [] }] }] }] let keys = ["state", "warningHighThreshold", "dangerHighThreshold"]; function populateState(children) { for (let item of children) Object.assign(item, populateState(item.children)) return children.length ? Object.assign(...keys.map(k => ({ [k]: Math.max(...children.map(o => o[k])) }))) : {} } console.log("Max Threshold:", populateState(input), "\\n\\nInput:", input)

Answer 4

Here is a non-mutating version that seems to do what you want, returning a new object with the maximum values rolled up to their ancestors:

 const collectMax = (xs) => xs .map (({children, kids = collectMax (children), ...rest}) => ({ ...rest, state: Math.max (rest.state, ... kids .map (k => k .state)), warningHighThreshold: Math .max (rest .warningHighThreshold, ... kids .map (k => k .warningHighThreshold)), dangerHighThreshold: Math .max (rest. dangerHighThreshold, ... kids .map (k => k .dangerHighThreshold)), children: kids })) const list = [{id: 100, idParent: null, anidatedView: null, state: null, warningHighThreshold: null, dangerHighThreshold: null, lvl: 1, children: [{id: 139, idParent: 100, anidatedView: null, state: null, warningHighThreshold: null, dangerHighThreshold: null, lvl: 2, children: [{id: 186, idParent: 139, anidatedView: 279, state: 15.58, warningHighThreshold: 80, dangerHighThreshold: 100, lvl: 3, children: []}, {id: 189, idParent: 139, anidatedView: 193, state: 40.65, warningHighThreshold: 80, dangerHighThreshold: 100, lvl: 3, children: []}]}, {id: 140, idParent: 100, anidatedView: null, state: null, warningHighThreshold: null, dangerHighThreshold: null, lvl: 2, children: [{id: 193, idParent: 140, anidatedView: 183, state: 65.41, warningHighThreshold: 92, dangerHighThreshold: 100, lvl: 3, children: []}]}, {id: 141, idParent: 100, anidatedView: null, state: null, warningHighThreshold: null, dangerHighThreshold: null, lvl: 2, children: [{id: 194, idParent: 141, anidatedView: 143, state: 60.77, warningHighThreshold: 90, dangerHighThreshold: 101, lvl: 3, children: []}, {id: 195, idParent: 141, anidatedView: 436, state: 59.13, warningHighThreshold: 90, dangerHighThreshold: 100, lvl: 3, children: []}]}]}] console .log ( collectMax (list) )

 .as-console-wrapper {max-height: 100% !important; top: 0}

We start by recursively applying the function to the children node, then combine our test value together with the appropriate value from each child, and take the maximum, assigning the current object that maximum for the appropriate property.

But I think it would be cleaner to pull out a helper function from this:

const collect = (ps, o, k) => Object.assign (... ps .map (p => ({
  [p]: Math.max (o [p], ... k .map (k => k [p]))
})))

const collectMax = (xs) => xs .map (({children, kids = collectMax (children), ...rest}) => ({
  ... rest,
  ... collect (['state', 'warningHighThreshold', 'dangerHighThreshold'], rest, kids),
  children: kids
}))

This does the same thing but slightly simplifies the code and makes it trivial to add new maximum-valued properties.