javascript get object keys in array

Question

I have an object similar to the one below:

const obj = {
 "test1": {
 "test12": "val1",
 "test13": {
 "test131": "val1",
 "test132": "val2"
 }
 },
 "test2": "val2"
}

I want to receive the keys as follows:

const keys = [["test1", "test12", "test13", "test131", "test132"], ["test2"]];

• Lux: What have you tried so far? What is not working? Recursion and Object.keys should help here.

Answer 1

You can recursively process the entries in the object, collecting keys as you go and flattening the result arrays at all levels other than the top:

const obj = {
 "test1": {
 "test12": "val1",
 "test13": {
 "test131": "val1",
 "test132": "val2"
 }
 },
 "test2": null,
 "test3": {
 "test31": "val3"
 },
 "test4": {
 "test41": [1, 2, 3, 4]
 }
}
const getKeys = (obj, flat = false) => {
 const keys = Object.entries(obj)
 .map(([k, v]) => v instanceof Object && !(v instanceof Array) ? [k, ...getKeys(v, true)] : [k])
 return flat ? keys.flat() : keys
}
const allKeys = getKeys(obj)
console.log(allKeys)

• Viktor Luft: This code will run into an error if one of the values is "null" and might not work as expected if one of the values would be an array.
• Nick: @ViktorLuft thanks for pointing that out. I've corrected the code to ensure it works correctly in those cases

Answer 2

Here you go:

const obj = {
 "test1": {
 "test12": "val1",
 "test13": {
 "test131": "val1",
 "test132": "val2"
 }
 },
 "test2": "val2"
};
const mapToKeys = ([key, value]) => {
 if (Object.prototype.toString.call(value) === '[object Object]') {
 return [key, ...getKeys(value)];
 }
 return [key];
};
const getKeys = (o) => Object.entries(o).flatMap(mapToKeys);
const keys = Object.entries(obj).map(mapToKeys);
console.log(keys);