How do I test for an empty JavaScript object?

Question 1

// because Object.keys(new Date()).length === 0; // we have to do some additional check obj // 👈 null and undefined check && Object.keys(obj).length === 0 && Object.getPrototypeOf(obj) === Object.prototype

Note, though, that this creates an unnecessary array (the return value of keys).

Pre-ECMA 5:

function isEmpty(obj) {   for(var prop in obj) {     if(Object.prototype.hasOwnProperty.call(obj, prop)) {       return false;     }   }    return JSON.stringify(obj) === JSON.stringify({}); }

jQuery:

jQuery.isEmptyObject({}); // true

lodash:

_.isEmpty({}); // true

Underscore:

_.isEmpty({}); // true

Hoek

Hoek.deepEqual({}, {}); // true

ExtJS

Ext.Object.isEmpty({}); // true

AngularJS (version 1)

angular.equals({}, {}); // true

Ramda

R.isEmpty({}); // true

Question 2

If ECMAScript 5 support is available, you can use Object.keys():

function isEmpty(obj) {     return Object.keys(obj).length === 0; }

For ES3 and older, there's no easy way to do this. You'll have to loop over the properties explicitly:

function isEmpty(obj) {     for(var prop in obj) {         if(obj.hasOwnProperty(prop))             return false;     }      return true; }

Question 3

For those of you who have the same problem but use jQuery, you can use jQuery.isEmptyObject.

Question 4

Performance

Today 2020.01.17, I performed tests on macOS High Sierra 10.13.6 on Chrome v79.0, Safari v13.0.4, and Firefox v72.0; for the chosen solutions.

Conclusions

Solutions based on for-in (A, J, L, M) are fastest
Solutions based on JSON.stringify (B, K) are slow
Surprisingly, the solution based on Object (N) is also slow

Details

There are 15 solutions presented in the snippet below. If you want to run a performance test on your machine, click HERE. This link was updated 2021.07.08, but tests originally were performed here - and results in the table above came from there (but now it looks like that service no longer works).

var log = (s, f) => console.log(`${s} --> {}:${f({})}  {k:2}:${f({ k: 2 })}`);  function A(obj) {   for (var i in obj) return false;   return true; }  function B(obj) {   return JSON.stringify(obj) === "{}"; }  function C(obj) {   return Object.keys(obj).length === 0; }  function D(obj) {   return Object.entries(obj).length === 0; }  function E(obj) {   return Object.getOwnPropertyNames(obj).length === 0; }  function F(obj) {   return Object.keys(obj).length === 0 && obj.constructor === Object; }  function G(obj) {   return typeof obj === "undefined" || !Boolean(Object.keys(obj)[0]); }  function H(obj) {   return Object.entries(obj).length === 0 && obj.constructor === Object; }  function I(obj) {   return Object.values(obj).every((val) => typeof val === "undefined"); }  function J(obj) {   for (const key in obj) {     if (hasOwnProperty.call(obj, key)) {       return false;     }   }   return true; }  function K(obj) {   for (var prop in obj) {     if (obj.hasOwnProperty(prop)) {       return false;     }   }   return JSON.stringify(obj) === JSON.stringify({}); }  function L(obj) {   for (var prop in obj) {     if (obj.hasOwnProperty(prop)) return false;   }   return true; }  function M(obj) {   for (var k in obj) {     if (obj.hasOwnProperty(k)) {       return false;     }   }   return true; }  function N(obj) {   return (     Object.getOwnPropertyNames(obj).length === 0 &&     Object.getOwnPropertySymbols(obj).length === 0 &&     Object.getPrototypeOf(obj) === Object.prototype   ); }  function O(obj) {   return !(Object.getOwnPropertyNames !== undefined     ? Object.getOwnPropertyNames(obj).length !== 0     : (function () {         for (var key in obj) break;         return key !== null && key !== undefined;       })()); }  log("A", A); log("B", B); log("C", C); log("D", D); log("E", E); log("F", F); log("G", G); log("H", H); log("I", I); log("J", J); log("K", K); log("L", L); log("M", M); log("N", N); log("O", O);

Question 5

You can use Underscore.js.

_.isEmpty({}); // true

How do I test for an empty JavaScript object?

Top 5 Answer for How do I test for an empty JavaScript object?

Performance

Conclusions

Details

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