Created
April 26, 2017 13:05
-
-
Save gnaeus/8eb0d34013c0cad4121ae81cb0a57a0a to your computer and use it in GitHub Desktop.
[JS] Speedup Redux normalized state 'byId' object transformation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
function protoMerge(source, changes, mergeThreshold = 100) { | |
let result; | |
const proto = Object.getPrototypeOf(source); | |
if (proto === Object.prototype || proto == null) { | |
// если source создан как object literal - то просто наследуемся от него | |
result = Object.create(source); | |
} else { | |
const sourceKeys = Object.keys(source); | |
const sourceLength = sourceKeys.length; | |
if (sourceLength < mergeThreshold) { | |
result = Object.create(proto); | |
// если размер объекта source меньше порогового значения | |
// - копируем только собственные свойства объекта source | |
for (let i = 0; i < sourceLength; i++) { | |
const key = sourceKeys[i] | |
result[key] = source[key]; | |
} | |
} else { | |
result = {}; | |
// иначе - копируем все перечисляемые свойства | |
// объекта source и его прототипа | |
for (const key in source) { | |
const value = source[key]; | |
// удаляем "пустые" свойства | |
if (typeof value !== "undefined") { | |
result[key] = value; | |
} | |
} | |
} | |
} | |
// копируем все перечисляемые свойства объекта changes | |
for (const key in changes) { | |
result[key] = changes[key]; | |
} | |
return result; | |
} |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment