Can I declare an array of integers in JSON without listing each element explicitly?

Question

I want a JSON array to contain all integers between 0 and 1000, but I don’t want to declare each element of that very long array individually. Is there a more economical/elegant way to declare that array in a JSON file?

Answer 1

No, you can't. However, JSON is just a convenient way to serialize and de-serialize data and has a mechanism to restore data, called reviver.

For the task you want, assuming you want the property numbers to be an array of 0 to 1000, I'd do this:

{
  "foo": "bar",
  "numbers": "0-1000"
}

And, when you parse it, you can use the reviver function:

const jsonString = `
{
  "foo": "bar",
  "numbers": "0-1000"  
}
`;

const obj = JSON.parse(jsonString, (key, val) => {
  if (key !== "numbers") return val;
  const res = [];
  const [ low, high ] = val.split("-");
  for (let i = +low; i <= +high; i++) {
    res.push(i);
  }
  return res;
});

console.log(obj);