Object.keys but not in order JS / TS

Use a Map if insertion order matters

If insertion order matters use a Map(), a map will retain the insertion order according the spec.

Demo

let map = new Map();
map.set('test', '...');
map.set('3', '...');
map.set('go', '...');
map.set('38', '...');

for( key of map.keys() )
  console.log( key )

You can use the Map object to iterate through keys in insertion order. As the MDN docs say,

The Map object holds key-value pairs and remembers the original insertion order of the keys. Any value (both objects and primitive values) may be used as either a key or a value. .... a for...of loop returns an array of [key, value] for each iteration.

If you can tolerate having leading zeros on the integer keys in the json, you could get it to work something like this:

const json = {
  "test" : "...",
  "03" : "...",
  "go" : "...",
  "038" : "..."
}
console.log(Object.keys(json))   //  ["test", "03", "go", "038"] in Chrome at least

The article here explains the ordering of object keys. Essentially, integers and integer-like strings go before strings, but string go in chronological order (order of insertion). If you put a leading zero on an (string) integer, it is treated as a string, not an integer, for the purposes of ordering.

This behaviour is I think dependent on the JS engine, but it is specified I think in ES6.

You can use a little hack by adding + to object number keys like shown below and then transform them to numbers again:

const json = {
  test: "...",
  "+3": "...",
  go: "...",
  "+38": "...",
};

for (let key in json) {
  let value = json[key];
  if (key[0] === "+") {
    key = +key;
  }

  console.log(key + ": " + value);
}