Object properties do not have order. I assume you want to re-name the properties, counting up from 0, but have the properties maintain the original relative ordering of their keys. (So the property with the smallest name is renamed to 0
, the second-to-smallest is 1
, etc.)
To do this, get all the property names, and sort the names numerically. Then, get all the values in the same over as their sorted property names. Finally, re-insert those property values with their new property names.
var itemsObj = obj["items"];
// get all names
var propertyNames = Object.keys(itemsObj);
// sort property names in numeric order: ["2", "4", "7"]
propertyNames.sort(function(a,b){ return a-b; });
// get property values, sorted by their property names
// ["2", "4", "7"] becomes [{ "id":122, .. }, { "id":15, ... }, { "id":78, ... }]
var values = propertyNames.map(function(propName) { return itemsObj[propName]; }
// clear out old property and add new property
for(var i=0; i<values.length; ++i) {
delete itemsObj[propertyNames[i]];
itemsObj[i] = values[i];
}