从JavaScript的递归函数返回对象数组

Question

I'm working on recursive functions.

I must push all objects that have the key "data: true" in an array. The console.log in the middle of my function gives me all those objects in separate arrays.

But I can't return an array with the objects at the end. What am I doing wrong? Thanks

 const entries = { root: { data: true, key: "root", text: "some text" }, test: { one: { two: { data: true, key: "test.one.two", text: "some text.again" }, three: { data: true, key: "test.one.three", text: "some.more.text" } }, other: { data: true, key: "test3", text: "sometext.text" } }, a: { b: { data: true, key: "ab", text: "abtext" }, c: { d: { data: true, key: "acd", text: "some.acd" } } } }; function recursiveFunc(data) { let tab = []; for (let property in data) { if (data.hasOwnProperty(property)) { if (data[property].data === true) { tab.push(data[property]); console.log("t", tab); } else { recursiveFunc(data[property]) } } } return tab } console.log(recursiveFunc(entries)); 

Answer 1

Add tab.concat() on the recursive call for join the items returned by the recursive fn.

 const entries = { root: { data: true, key: "root", text: "some text" }, test: { one: { two: { data: true, key: "test.one.two", text: "some text.again" }, three: { data: true, key: "test.one.three", text: "some.more.text" } }, other: { data: true, key: "test3", text: "sometext.text" } }, a: { b: { data: true, key: "ab", text: "abtext" }, c: { d: { data: true, key: "acd", text: "some.acd" } } } }; function recursiveFunc(data) { let tab = []; for (let property in data) { if (data.hasOwnProperty(property)) { if (data[property].data === true) { tab.push(data[property]); console.log("t", tab); } else { tab = tab.concat(recursiveFunc(data[property])); } } } return tab } console.log(recursiveFunc(entries)); 

Answer 2

You can pass an array as second argument that will act as an accumulator.

Plus, I fixed your function that loops infinitely when data = false :

function recursiveFunc(data, acc) {
  for (let property in data) {
    if (data.hasOwnProperty(property) && typeof data[property] === "object") {

      var current = data[property];

      if (current.data === true) {
        acc.push(current);
      } else {
        recursiveFunc(current, acc)
      }

    }
  }
}

Usage:

var results = [];
recursiveFunc(entries, results);
console.log(results);

Answer 3

You could use a global variable.

const entries = { ... };


var tab = [];

function getTab(data) {
    tab = [];
    recursiveFunc(data);
    return tab;
}
function recursiveFunc(data) {
  for (let property in data) {
    if (data.hasOwnProperty(property) && typeof data[property] === "object") {
      if (data[property].data === true) {
        tab.push(data[property]);
      } else {
        recursiveFunc(data[property])
      }
    }
  }
}

getTab(entries);