Im trying to create an array in JS and then loop through it

Question

I have data saved in "localStorage".

Now i'd like to put that data into a JS array so that i can sort it and then output it.

//CREATE ARRAY
var localStorage_arr = [];

//LOOP THREW localStorage
Object.keys(localStorage).forEach(function(key){

  //GET LOCALSTORAGE ITEM
  var item = JSON.parse(localStorage.getItem(key));

  //SET ARRAY KEY AND CREATE MULTIDIMENSIONAL ARRAY
  localStorage_arr[key] = [];

  //ADD SOME DATA
  localStorage_arr[key]['art_id'] = item.art_id;
  localStorage_arr[key]['art_nr'] = item.art_nr;
});

//SORT ARRAY    
localStorage_arr.sort();

//CONSOLE.LOG ARRAY
console.log(localStorage_arr)

//IN LOG:
[1614851259727: Array(0), 1614849876677: Array(0), 1614849865169: Array(0), 1614849873617: Array(0), 1614849870613: Array(0)]
1614849865169: [art_id: 2110, art_nr: "01", article: "Test", balance: 362, …]
1614849870613: [art_id: 2110, art_nr: "01", article: "Test", balance: 362, …]
1614849873617: [art_id: 2110, art_nr: "01", article: "Test", balance: 362, …]
1614849876677: [art_id: 2110, art_nr: "01", article: "Test", balance: 362, …]
1614851259727: [art_id: 2110, art_nr: "01", article: "Test", balance: 380, …]

Question one: Why does it say: Array(0) ?

Later i try to loop threw my array:

//LOOP THREW localStorage_arr
localStorage_arr.forEach(function (item, index) {
    //console.log(item, index);
});

//IN LOG: nothing..

Why can't i loop threw the array?

@lissettdm Yes, Key is the date in milliseconds like: 1614851259727 — Björn C
– Björn C, Commented Mar 4, 2021 at 12:55
So, you are assuming that key was the element position right? — lissettdm
– lissettdm, Commented Mar 4, 2021 at 12:56
@lissettdm The reason why i'm doing a array of the localStorage is because i need to sort the data by it's key. localStorage doesn't sort or order the keys. So i put the date in millisenconds as a key, for when i add something to the localStorage, then i want to display them in the order it was added. — Björn C
– Björn C, Commented Mar 4, 2021 at 13:01

n-- · Accepted Answer · 2021-03-04 12:29:31Z

1

it is because of how javascript array work, see JavaScript Array

Arrays cannot use strings as element indexes (as in an associative array) but must use integers. Setting or accessing via non-integers using bracket notation (or dot notation) will not set or retrieve an element from the array list itself, but will set or access a variable associated with that array's object property collection.

answered Mar 4, 2021 at 12:29

n--

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2 Comments

Björn C Over a year ago

But the key i set is: 1614851259727 so its a number, right?

n-- Over a year ago

@Björn C yes, but it is a BigInt value, but array keys must be of uint32, see explanation here:developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…

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