Generate a flat array of ids from a multilevel tree using reduce function with recursion?

I am trying to implement a user hierarchy using the js library orgChart. by getHierarchy() method in the library is outputting a object like the following.

var datascource = {
            "id": "1",
            "children": [{
                "id": "2"
            }, {
                "id": "3",
                "children": [{
                    "id": "4"
                }, {
                    "id": "5",
                    "children": [{
                        "id": "6"
                    }, {
                        "id": "7"
                    }]
                }]
            }, {
                "id": "10"
            }, {
                "id": "12"
            }]
        };

I want to generate flat array from ids in the tree. ex: //["1", "2", "3", "4", "5", "6", "7", "10", "12"]

I came up with,

function getNestedArraysOfIds(node) {
    if (node.children == undefined) {
        return [node.id];
    } else {
        return [node.id,...node.children.map(subnode => (subnode.children==undefined) ? subnode.id: getNestedArraysOfIds(subnode))];
    }
}

function getIds(array) {
        return array.reduce((acc, subArray) =>
            (Array.isArray(subArray)) ? [...acc, ...getIds(subArray)] : [...acc, subArray]);
    }

var idArrays = getNestedArraysOfIds(datascource );
var ids = getIds(idArrays); //["1", "2", "3", "4", "5", "6", "7", "10", "12"]

I have try to do it with single reduce function but I end up writing two functions both of them are recursive. Is there much elegant and effective way to do it with single reduce function?

Thank you in advance.

You could flat the children by taking a mapping with concat.

function getFlat({ id, children = [] }) {
    return [id].concat(...children.map(getFlat));
}

var data = { id: "1", children: [{ id: "2" }, { id: "3", children: [{ id: "4" }, { id: "5", children: [{ id: "6" }, { id: "7" }] }] }, { id: "10" }, { id: "12" }] };

console.log(getFlat(data));

Same with a reduce function

function getFlat({ id, children = [] }) {
    return children.reduce((r, o) => [...r, ...getFlat(o)], [id]);
}

var data = { id: "1", children: [{ id: "2" }, { id: "3", children: [{ id: "4" }, { id: "5", children: [{ id: "6" }, { id: "7" }] }] }, { id: "10" }, { id: "12" }] };

console.log(getFlat(data));