allows memoization of circular structures

.gitignore

@@ -3,3 +3,4 @@ node_modules/
 npm-debug.log
 .DS_Store
 coverage/
+.vscode

benchmark/cache/index.js

@@ -1,3 +1,4 @@
+'use stict'
 const ora = require('ora')
 const Table = require('cli-table2')
 const debug = require('logdown')()

benchmark/index.js

@@ -1,3 +1,4 @@
+'use stict'
 const ora = require('ora')
 const Table = require('cli-table2')
 const debug = require('logdown')()

benchmark/recursive-solo.js

@@ -1,3 +1,4 @@
+'use stict'
 const ora = require('ora')
 const logger = require('logdown')()
 const Table = require('cli-table2')

benchmark/strategy/index.js

@@ -1,3 +1,4 @@
+'use stict'
 const ora = require('ora')
 const Table = require('cli-table2')
 const debug = require('logdown')()

benchmark/strategy/partial-application.js

@@ -22,7 +22,10 @@ function strategy (fn, options) {
     return cache.get(cacheKey)
   }
 
-  function variadic (fn, cache, serializer, ...args) {
+  function variadic (fn, cache, serializer) {
+    for (var _len = arguments.length, args = Array(_len > 3 ? _len - 3 : 0), _key = 3; _key < _len; _key++) {
+      args[_key - 3] = arguments[_key];
+    }
     var cacheKey = serializer(args)
 
     if (!cache.has(cacheKey)) {
@@ -34,9 +37,9 @@ function strategy (fn, options) {
     return cache.get(cacheKey)
   }
 
-  var memoized = fn.length === 1
-    ? monadic
-    : variadic
+  var memoized = fn.length === 1 ?
+    monadic :
+    variadic
 
   memoized = memoized.bind(this, fn, options.cache.create(), options.serializer)
   memoized.label = 'strategy: Partial application, cache: ' + options.cache.label + ', serializer: ' + options.serializer.label

src/delme.js

@@ -0,0 +1,16 @@
+var memoize = require('../src')
+
+var circular = {
+  a: 'foo'
+}
+circular.b = circular
+
+function circularFunction (a) {
+  return a.a
+}
+
+var memoizedCircularFunction = memoize(circularFunction)
+
+// Assertions
+var one = memoizedCircularFunction(circular)
+var two = memoizedCircularFunction(circular)

src/index.js

@@ -1,3 +1,5 @@
+'use strict'
+const util = require('util')
 //
 // Main
 //
@@ -57,7 +59,11 @@ function strategyDefault (fn, options) {
     return cache.get(cacheKey)
   }
 
-  function variadic (fn, cache, serializer, ...args) {
+  function variadic (fn, cache, serializerrgs) {
+    for (var _len = arguments.length, args = Array(_len > 3 ? _len - 3 : 0), _key = 3; _key < _len; _key++) {
+      args[_key - 3] = arguments[_key];
+    }
+
     var cacheKey = serializer(args)
 
     if (!cache.has(cacheKey)) {
@@ -69,9 +75,9 @@ function strategyDefault (fn, options) {
     return cache.get(cacheKey)
   }
 
-  var memoized = fn.length === 1
-    ? monadic
-    : variadic
+  var memoized = fn.length === 1 ?
+    monadic :
+    variadic
 
   memoized = memoized.bind(
     this,
@@ -89,36 +95,75 @@ function strategyDefault (fn, options) {
 // Serializer
 //
 
-function serializerDefault (...args) {
-  return JSON.stringify(args)
+function customReplacer(args) {
+  var cache = [];
+  const replacer = function (key, value) {
+    if (typeof value === 'object' && value !== null) {
+      if (cache.indexOf(value) !== -1) {
+        // Circular reference found, discard key
+        return
+      }
+      // Store value in our collection
+      cache.push(value)
+    }
+  }
+  cache = null // Enable garbage collection
+  return replacer
+}
+
+//
+// Serializer
+//
+
+function serializerDefault () {
+  for (var _len = arguments.length, args = Array(_len), _key = 0; _key < _len; _key++) {
+    args[_key] = arguments[_key]
+  }
+
+  try {
+    // try the fastest way first.
+    return JSON.stringify(args)
+  } catch (error) {
+    if (error instanceof TypeError &&
+      error.message === 'Converting circular structure to JSON') {
+      // if node
+      if (util && util.inspect) {
+        return JSON.stringify(util.inspect(args))
+      } else {
+        return JSON.stringify(args, customReplacer)
+      }
+    } else {
+      throw error // let others bubble up
+    }
+  }
 }
 
 //
 // Cache
 //
 
 class ObjectWithoutPrototypeCache {
-  constructor () {
+  constructor() {
     this.cache = Object.create(null)
   }
 
-  has (key) {
+  has(key) {
     return (key in this.cache)
   }
 
-  get (key) {
+  get(key) {
     return this.cache[key]
   }
 
-  set (key, value) {
+  set(key, value) {
     this.cache[key] = value
   }
 
-  delete (key) {
+  delete(key) {
     delete this.cache[key]
   }
 }
 
 const cacheDefault = {
   create: () => new ObjectWithoutPrototypeCache()
-}
+}

src/index.test.js

@@ -144,3 +144,21 @@ test('inject custom serializer', function () {
 
   expect(serializerMethodExecutionCount).toBe(2)
 })
+
+test('memoize circular JSON', function () {
+  var circular = {
+    a: 'foo'
+  }
+  circular.b = circular
+
+  function circularFunction(a) {
+    return a.a
+  }
+
+  var memoizedCircularFunction = memoize(circularFunction)
+
+  // Assertions
+
+  expect(memoizedCircularFunction(circular)).toBe("foo")
+  expect(memoizedCircularFunction(circular)).toBe("foo")
+})