index.js

module.exports = stringify
stringify.default = stringify
stringify.stable = deterministicStringify
stringify.stableStringify = deterministicStringify

var LIMIT_REPLACE_NODE = '[...]'
var CIRCULAR_REPLACE_NODE = '[Circular]'

var arr = []
var replacerStack = []

function defaultOptions () {
  return {
    depthLimit: Number.MAX_SAFE_INTEGER,
    edgesLimit: Number.MAX_SAFE_INTEGER
  }
}

// Regular stringify
function stringify (obj, replacer, spacer, options) {
  if (typeof options === 'undefined') {
    options = defaultOptions()
  }

  decirc(obj, '', 0, [], undefined, 0, options)
  var res
  try {
    if (replacerStack.length === 0) {
      res = JSON.stringify(obj, replacer, spacer)
    } else {
      res = JSON.stringify(obj, replaceGetterValues(replacer), spacer)
    }
  } catch (_) {
    return JSON.stringify('[unable to serialize, circular reference is too complex to analyze]')
  } finally {
    while (arr.length !== 0) {
      var part = arr.pop()
      if (part.length === 4) {
        Object.defineProperty(part[0], part[1], part[3])
      } else {
        part[0][part[1]] = part[2]
      }
    }
  }
  return res
}

function setReplace (replace, val, k, parent) {
  var propertyDescriptor = Object.getOwnPropertyDescriptor(parent, k)
  if (propertyDescriptor.get !== undefined) {
    if (propertyDescriptor.configurable) {
      Object.defineProperty(parent, k, { value: replace })
      arr.push([parent, k, val, propertyDescriptor])
    } else {
      replacerStack.push([val, k, replace])
    }
  } else {
    parent[k] = replace
    arr.push([parent, k, val])
  }
}

function decirc (val, k, edgeIndex, stack, parent, depth, options) {
  depth += 1
  var i
  if (typeof val === 'object' && val !== null) {
    for (i = 0; i < stack.length; i++) {
      if (stack[i] === val) {
        setReplace(CIRCULAR_REPLACE_NODE, val, k, parent)
        return
      }
    }

    if (
      typeof options.depthLimit !== 'undefined' &&
      depth > options.depthLimit
    ) {
      setReplace(LIMIT_REPLACE_NODE, val, k, parent)
      return
    }

    if (
      typeof options.edgesLimit !== 'undefined' &&
      edgeIndex + 1 > options.edgesLimit
    ) {
      setReplace(LIMIT_REPLACE_NODE, val, k, parent)
      return
    }

    stack.push(val)
    // Optimize for Arrays. Big arrays could kill the performance otherwise!
    if (Array.isArray(val)) {
      for (i = 0; i < val.length; i++) {
        decirc(val[i], i, i, stack, val, depth, options)
      }
    } else {
      var keys = Object.keys(val)
      for (i = 0; i < keys.length; i++) {
        var key = keys[i]
        decirc(val[key], key, i, stack, val, depth, options)
      }
    }
    stack.pop()
  }
}

// Stable-stringify
function compareFunction (a, b) {
  if (a < b) {
    return -1
  }
  if (a > b) {
    return 1
  }
  return 0
}

function deterministicStringify (obj, replacer, spacer, options) {
  if (typeof options === 'undefined') {
    options = defaultOptions()
  }

  var tmp = deterministicDecirc(obj, '', 0, [], undefined, 0, options) || obj
  var res
  try {
    if (replacerStack.length === 0) {
      res = JSON.stringify(tmp, replacer, spacer)
    } else {
      res = JSON.stringify(tmp, replaceGetterValues(replacer), spacer)
    }
  } catch (_) {
    return JSON.stringify('[unable to serialize, circular reference is too complex to analyze]')
  } finally {
    // Ensure that we restore the object as it was.
    while (arr.length !== 0) {
      var part = arr.pop()
      if (part.length === 4) {
        Object.defineProperty(part[0], part[1], part[3])
      } else {
        part[0][part[1]] = part[2]
      }
    }
  }
  return res
}

function deterministicDecirc (val, k, edgeIndex, stack, parent, depth, options) {
  depth += 1
  var i
  if (typeof val === 'object' && val !== null) {
    for (i = 0; i < stack.length; i++) {
      if (stack[i] === val) {
        setReplace(CIRCULAR_REPLACE_NODE, val, k, parent)
        return
      }
    }
    try {
      if (typeof val.toJSON === 'function') {
        return
      }
    } catch (_) {
      return
    }

    if (
      typeof options.depthLimit !== 'undefined' &&
      depth > options.depthLimit
    ) {
      setReplace(LIMIT_REPLACE_NODE, val, k, parent)
      return
    }

    if (
      typeof options.edgesLimit !== 'undefined' &&
      edgeIndex + 1 > options.edgesLimit
    ) {
      setReplace(LIMIT_REPLACE_NODE, val, k, parent)
      return
    }

    stack.push(val)
    // Optimize for Arrays. Big arrays could kill the performance otherwise!
    if (Array.isArray(val)) {
      for (i = 0; i < val.length; i++) {
        deterministicDecirc(val[i], i, i, stack, val, depth, options)
      }
    } else {
      // Create a temporary object in the required way
      var tmp = {}
      var keys = Object.keys(val).sort(compareFunction)
      for (i = 0; i < keys.length; i++) {
        var key = keys[i]
        deterministicDecirc(val[key], key, i, stack, val, depth, options)
        tmp[key] = val[key]
      }
      if (typeof parent !== 'undefined') {
        arr.push([parent, k, val])
        parent[k] = tmp
      } else {
        return tmp
      }
    }
    stack.pop()
  }
}

// wraps replacer function to handle values we couldn't replace
// and mark them as replaced value
function replaceGetterValues (replacer) {
  replacer =
    typeof replacer !== 'undefined'
      ? replacer
      : function (k, v) {
        return v
      }
  return function (key, val) {
    if (replacerStack.length > 0) {
      for (var i = 0; i < replacerStack.length; i++) {
        var part = replacerStack[i]
        if (part[1] === key && part[0] === val) {
          val = part[2]
          replacerStack.splice(i, 1)
          break
        }
      }
    }
    return replacer.call(this, key, val)
  }
}