Try to get key values recursively from JSON in Angular 5 - json

Question

I want to retrieve all the key values from a JSON file. For example in :
{
"total_count": 6,
"incomplete_results": false,
"items": [
{
"url": "https://api.github.com/repos/Samhot/GenIHM/issues/6",
"id": 293237635,
"number": 6,
"title": "Rechercher des documents",
"user": {
"login": "Samhot",
"id": 7148311
]
}
I would like to get :
["total_count", "incomplete_results", "items", "url", "url", "number", "title", "user", "login", "id"]
I have a function which return the content of my JSON in an observable :
getConfig(): Observable<any> {
return this.http.get<any>(this.myURL);
}
After that the data are reformated with .map to get only the keys with the Object.keys() function :
merge()
.pipe(
startWith({}),
switchMap(() => {
return this.getConfig();
}),
map(data => {
return Object.keys(data.items[0]);
}
)
)
.subscribe(data => {
this.dispo = data;
});
My problem is that i get only the keys that are in the level of the JSON I told
(data.items[0]) and not the ascendants or the descendants.
Of course I can create multiple requests but it asks to know in advance the structure of the JSON, what I want is to make it generic ...
How can I do to have an array with with all of my keys regardless of the structure of the JSON ?
Thanks in advance !

Answer 1

You would need to do a recursive function like:
function getDeepKeys(obj) {
const keys = Object.keys(obj);
const childKeys = keys
.map(key => obj[key])
.map(
value =>
Array.isArray(value)
? getDeepKeys(value[0])
: typeof value === "object"
? getDeepKeys(value)
: []
)
.reduce((acc, keys) => [...acc, ...keys], []);
return [...keys, ...childKeys];
}
const obj = {
total_count: 6,
incomplete_results: false,
items: [
{
url: "https://api.github.com/repos/Samhot/GenIHM/issues/6",
id: 293237635,
number: 6,
title: "Rechercher des documents",
user: {
login: "Samhot",
id: 7148311
}
},
{
url: "https://api.github.com/repos/Samhot/GenIHM/issues/6",
id: 293237635,
number: 6,
title: "Rechercher des documents",
user: {
login: "Samhot",
id: 7148311
}
}
]
};
console.log(getDeepKeys(obj));
Which then you would use like map(getDeepKeys). Note that this function assumes all the items in your array have the same schema.