JSON.stringify for ExtendScript(ES3)

json.ts

const jsonStringify = (() => {
  const q = (s: string) => '"' + s + '"'
  const sp = (indent: number, lv: number) => (indent ? '\n' : '') + Array(lv * indent + 1).join(' ')
  const printObj = (lp: string, tokens: string[], rp: string, indent: number, lv: number) => {
    if (!tokens.length) return lp + rp
    return lp + sp(indent, lv + 1) + tokens.join(',' + sp(indent, lv + 1)) + sp(indent, lv) + rp
  }
  const stringify = (v: JsonValue, indent: number, lv: number, path: any[]): string => {
    if (!(v instanceof Object)) return typeof v === 'string' ? q(v) : '' + v
    for (let o of path) if (v === o) return q('[CIRCULAR]')
    if (v instanceof Function) return q('[Function: ' + v.name + ']')
    const sv: string[] = []
    if (v instanceof Array) {
      for (let e of v) sv.push(stringify(e, indent, lv + 1, path.concat([v])))
      return printObj('[', sv, ']', indent, lv)
    }
    for (let k in v) sv.push(q(k) + ': ' + stringify(v[k], indent, lv + 1, path.concat([v])))
    return printObj('{', sv, '}', indent, lv)
  }
  return (v: JsonValue, indent?: number) => stringify(v, indent || 0, 0, [])
})()