JSFiddle - React, Tailwind, and code Playground

HTML

Old:
<pre id="old"></pre>

<br />New:
<pre id="new"></pre>

JavaScript

var object = {
    "items": {
        "2": {
            "id": 122,
                "product_id": "DE",
                "price": "9.35"
        },
            "4": {
            "id": 15,
                "product_id": "CH",
                "price": "8.00"
        },
            "7": {
            "id": 78,
                "product_id": "CH",
                "price": "3.00"
        }
    },
        "total_price": "20.35",
        "item_count": 2,
        "unit": "CHF"
};

function format(object) {
    var items = {};
    var i = 0;
    for (var index in object.items) {
        items[i] = object.items[index];
        i++;
    }
    object.items = items;
}

$('#old').html(JSON.stringify(object, null, 4));

// Change object
format(object);
$('#new').html(JSON.stringify(object, null, 4));