index.js

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

var arr = []
var replacerStack = []

// Regular stringify
function stringify (obj, replacer, spacer) {
  decirc(obj, '', [], undefined)
  var res
  if (replacerStack.length === 0) {
    res = JSON.stringify(obj, replacer, spacer)
  } else {
    res = JSON.stringify(obj, replaceGetterValues(replacer), spacer)
  }
  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 decirc (val, k, stack, parent) {
  var i
  if (typeof val === 'object' && val !== null) {
    for (i = 0; i < stack.length; i++) {
      if (stack[i] === val) {
        var propertyDescriptor = Object.getOwnPropertyDescriptor(parent, k)
        if (propertyDescriptor.get !== undefined) {
          if (propertyDescriptor.configurable) {
            Object.defineProperty(parent, k, { value: '[Circular]' })
            arr.push([parent, k, val, propertyDescriptor])
          } else {
            replacerStack.push([val, k])
          }
        } else {
          parent[k] = '[Circular]'
          arr.push([parent, k, val])
        }
        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, stack, val)
      }
    } else {
      var keys = Object.keys(val)
      for (i = 0; i < keys.length; i++) {
        var key = keys[i]
        decirc(val[key], key, stack, val)
      }
    }
    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) {
  var tmp = deterministicDecirc(obj, '', [], undefined) || obj
  var res
  if (replacerStack.length === 0) {
    res = JSON.stringify(tmp, replacer, spacer)
  } else {
    res = JSON.stringify(tmp, replaceGetterValues(replacer), spacer)
  }
  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, stack, parent) {
  var i
  if (typeof val === 'object' && val !== null) {
    for (i = 0; i < stack.length; i++) {
      if (stack[i] === val) {
        var propertyDescriptor = Object.getOwnPropertyDescriptor(parent, k)
        if (propertyDescriptor.get !== undefined) {
          if (propertyDescriptor.configurable) {
            Object.defineProperty(parent, k, { value: '[Circular]' })
            arr.push([parent, k, val, propertyDescriptor])
          } else {
            replacerStack.push([val, k])
          }
        } else {
          parent[k] = '[Circular]'
          arr.push([parent, k, val])
        }
        return
      }
    }
    if (typeof val.toJSON === 'function') {
      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, stack, val)
      }
    } 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, stack, val)
        tmp[key] = val[key]
      }
      if (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 [Circular]
function replaceGetterValues (replacer) {
  replacer = 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 = '[Circular]'
          replacerStack.splice(i, 1)
          break
        }
      }
    }
    return replacer.call(this, key, val)
  }
}