circular-json-es6/index.js

circular JSON.stringify and JSON.parse, for environments with native ES6 Map

function encode (data, replacer, list, seen) {
  var stored, key, value, i, l
  var seenIndex = seen.get(data)
  if (seenIndex != null) {
    return seenIndex
  }
  var index = list.length
  var proto = Object.prototype.toString.call(data)
  if (proto === '[object Object]') {
    stored = {}
    seen.set(data, index)
    list.push(stored)
    var keys = Object.keys(data)
    for (i = 0, l = keys.length; i < l; i++) {
      key = keys[i]
      value = data[key]
      if (replacer) value = replacer.call(data, key, value)
      stored[key] = encode(value, replacer, list, seen)
    }
  } else if (proto === '[object Array]') {
    stored = []
    seen.set(data, index)
    list.push(stored)
    for (i = 0, l = data.length; i < l; i++) {
      value = data[i]
      if (replacer) value = replacer.call(data, i, value)
      stored[i] = encode(value, replacer, list, seen)
    }
  } else {
    list.push(data)
  }
  return index
}

function decode (list, reviver) {
  var i = list.length
  var j, k, data, key, value, proto
  while (i--) {
    data = list[i]
    proto = Object.prototype.toString.call(data)
    if (proto === '[object Object]') {
      var keys = Object.keys(data)
      for (j = 0, k = keys.length; j < k; j++) {
        key = keys[j]
        value = list[data[key]]
        if (reviver) value = reviver.call(data, key, value)
        data[key] = value
      }
    } else if (proto === '[object Array]') {
      for (j = 0, k = data.length; j < k; j++) {
        value = list[data[j]]
        if (reviver) value = reviver.call(data, j, value)
        data[j] = value
      }
    }
  }
}

exports.stringify = function stringify (data, replacer, space) {
  try {
    return arguments.length === 1
      ? JSON.stringify(data)
      : JSON.stringify(data, replacer, space)
  } catch (e) {
    return exports.stringifyStrict(data, replacer, space)
  }
}

exports.parse = function parse (data, reviver) {
  var hasCircular = /^\s/.test(data)
  if (!hasCircular) {
    return arguments.length === 1
      ? JSON.parse(data)
      : JSON.parse(data, reviver)
  } else {
    var list = JSON.parse(data)
    decode(list, reviver)
    return list[0]
  }
}

exports.stringifyStrict = function stringifyStrict (data, replacer, space) {
  var list = []
  encode(data, replacer, list, new Map())
  return space
    ? ' ' + JSON.stringify(list, null, space)
    : ' ' + JSON.stringify(list)
}