@dbl0null/slow-json-stringify/src/_select.mjs

The slow.. well actually fastest JSON stringifier in the galaxy.

/**
 * `select` function takes all the possible chunks from the
 * current index and set the more appropriate one in relation
 * to the current `value` and the `flag` state.
 *
 * => This approach avoids the use of Regex during serialization.
 *
 * @param {any} chunks - value to serialize.
 */
const _select = chunks => (value, index) => {
  const chunk = chunks[index]

  if (value !== undefined) {
    if (chunk.flag) {
      return chunk.prevUndef + value
    }
    return chunk.pure + value
  }

  // If the current value is undefined set a flag on the next
  // chunk stating that the previous prop is undefined.
  chunks[index + 1].flag = true

  if (chunk.flag) {
    return chunk.bothUndef
  }
  return chunk.isUndef
}

export { _select }