rebuild array from tree es6

listToFlatArray.js

export function listToFlatArray(treeStructure) {
    let flatten = (children, extractChildren, level, parent) => Array.prototype.concat.apply(
      children.map(x => ({ ...x, level: level || 1, parent: parent || null })), 
      children.map(x => flatten(extractChildren(x) || [], extractChildren, (level || 1) + 1, x.id))
    );

    let extractChildren = x => x.children;
  
    return flatten(extractChildren(treeStructure), extractChildren).map(x => delete x.children && x);
}

/*
ex:

let treeStructure = {
    "children": [{
        "id": 1,
        "title": "home",
        "parent": null,
        "children": []
    }, {
        "id": 2,
        "title": "about",
        "parent": null,
        "children": [{
            "id": 3,
            "title": "team",
            "parent": 2,
            "children": [{
            "id": 5,
            "title": "company",
            "parent": null,
            "children": []
        }]
        }, {
            "id": 4,
            "title": "company",
            "parent": 2,
            "children": []
        }]
    }]
};

listToFlatArray(treeStructure);
*/