循環参照を含むオブジェクトのJSON.stringify

index.js

;(function (global) {
    'use strict'
    var isBrowser = !! global.self
    var isWorker  = !! global.workerLocation
    var isNodeJS  = !! global.global

    function stringify (o, rep, sp) {
        return JSON.stringify(o, (function (m) {
            return function (key, val) {
                if (val instanceof Error) return val.toString()
                if (indexOf(m, val) !== -1) return '[Circular]'
                val && 'object' === typeof val && m.push(val)
                return 'function' === typeof rep ? rep(key, val) : val
            }
        })([]), sp)
    }

    function indexOf (arry, target) {
        if ('function' === typeof arry.indexOf) return arry.indexOf(target)
        for (var i = 0, len = arry.length; i < len; i++) {
            if (arry[i] === target) return i
        }
        return -1
    }

    if (isNodeJS) {
        module.exports.stringify = stringify
    } else {
        global['Message'] = {
            stringify: stringify
        }
    }
})(this.self || global)

test.js

var test = require('tape')
var mod
var circular = '[Circular]'

test('load module', function (t) {
    mod = require('..')
    t.ok(mod, 'var mod = require("..")')
    t.is(typeof mod.stringify, 'function', 'typeof mod.stringify === "function"')
    t.end()
})

test('循環参照しているプロパティは 文字列 "' + circular + '" に置き換わる', function (t) {
    var obj = {a: 3}
    obj.self = obj
    obj.list = [obj, obj]

    var testObj = {
        a: 3
      , self: circular
      , list: [circular, circular]
    }

    t.is(JSON.stringify(testObj, null, 2)
      , mod.stringify(obj, null, 2)
      , mod.stringify(obj, null, 2)
    )
    t.end()
})

test('エラーオブジェクトは "name: message" に置き換わる', function (t) {
    var e = new TypeError('oh no!')
    var obj = {error: e}
    t.is(mod.stringify(obj)
      , '{"error":"TypeError: oh no!"}'
      , mod.stringify(obj)
    )
    t.end()
})