How to put a Map/JSON object containing array values into local storage

Question

I want to store the following into local storage with a structure like so:

{
  "stuff": [
    {
      "user1": {
        "numbers": [
          1,
          2,
          3
        ]
      },
      "user2": {
        "numbers": [
          2
        ]
      }
    }
  ]
}

How would I go about doing this?

Your structure is invalid. An array doesn't contain key/value-pairs. Could you fix the structure? — 3limin4t0r
– 3limin4t0r, Commented Jun 18, 2020 at 16:21

Pampapathi · Accepted Answer · 2022-07-25 09:35:14Z

2

This works for me.

    (() => {
  // ok
  const map = new Map();
  map.set(1, {id: 1, name: 'eric'});
  // Map(1) {1 => {…}}
  localStorage.setItem('app', JSON.stringify([...map]));
  // undefined
  const newMap = new Map(JSON.parse(localStorage.getItem('app')));
  // Map(1) {1 => {…}} ✅
})();

answered Jul 25, 2022 at 9:35

Pampapathi

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Comments

Cagri Tacyildiz · Accepted Answer · 2020-06-18 16:15:23Z

1

to save

localStorage.setItem("name",JSON.stringify(Map));

to read

JSON.parse(localStorage.getItem("name"));

answered Jun 18, 2020 at 16:15

Cagri Tacyildiz

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3 Comments

chingu Over a year ago

I have tried just doing JSON.stringify(Map) and it is persisting as {} meaning its showing up as empty for some reason

Cagri Tacyildiz Over a year ago

Your object need to be like [{"userID1": [1, 2, 3]}, {"userID2": [1, 2, 3]}] and if problem is Map then try to change its name

Pampapathi Over a year ago

For me too, it is not stringifying the Map object. It is stringinfying as {}.

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