Is object empty?
JavascriptJavascript Problem Overview
What is the fastest way to check if an object is empty or not?
Is there a faster and better way than this:
function count_obj(obj){
var i = 0;
for(var key in obj){
++i;
}
return i;
}
Javascript Solutions
Solution 1 - Javascript
For ECMAScript5 (not supported in all browsers yet though), you can use:
Object.keys(obj).length === 0
Solution 2 - Javascript
I'm assuming that by empty you mean "has no properties of its own".
// Speed up calls to hasOwnProperty
var hasOwnProperty = Object.prototype.hasOwnProperty;
function isEmpty(obj) {
// null and undefined are "empty"
if (obj == null) return true;
// Assume if it has a length property with a non-zero value
// that that property is correct.
if (obj.length > 0) return false;
if (obj.length === 0) return true;
// If it isn't an object at this point
// it is empty, but it can't be anything *but* empty
// Is it empty? Depends on your application.
if (typeof obj !== "object") return true;
// Otherwise, does it have any properties of its own?
// Note that this doesn't handle
// toString and valueOf enumeration bugs in IE < 9
for (var key in obj) {
if (hasOwnProperty.call(obj, key)) return false;
}
return true;
}
Examples:
isEmpty(""), // true
isEmpty(33), // true (arguably could be a TypeError)
isEmpty([]), // true
isEmpty({}), // true
isEmpty({length: 0, custom_property: []}), // true
isEmpty("Hello"), // false
isEmpty([1,2,3]), // false
isEmpty({test: 1}), // false
isEmpty({length: 3, custom_property: [1,2,3]}) // false
If you only need to handle ECMAScript5 browsers, you can use Object.getOwnPropertyNames instead of the hasOwnProperty loop:
if (Object.getOwnPropertyNames(obj).length > 0) return false;
This will ensure that even if the object only has non-enumerable properties isEmpty will still give you the correct results.
Solution 3 - Javascript
EDIT: Note that you should probably use ES5 solution instead of this since ES5 support is widespread these days. It still works for jQuery though.
Easy and cross-browser way is by using jQuery.isEmptyObject:
if ($.isEmptyObject(obj))
{
// do something
}
More: http://api.jquery.com/jQuery.isEmptyObject/
You need jquery though.
Solution 4 - Javascript
Underscore and lodash each have a convenient isEmpty() function, if you don't mind adding an extra library.
_.isEmpty({});
Solution 5 - Javascript
Lets put this baby to bed; tested under Node, Chrome, Firefox and IE 9, it becomes evident that for most use cases:
- (for...in...) is the fastest option to use!
- Object.keys(obj).length is 10 times slower for empty objects
- JSON.stringify(obj).length is always the slowest (not surprising)
- Object.getOwnPropertyNames(obj).length takes longer than Object.keys(obj).length can be much longer on some systems.
Bottom line performance wise, use:
function isEmpty(obj) {
for (var x in obj) { return false; }
return true;
}
or
function isEmpty(obj) {
for (var x in obj) { if (obj.hasOwnProperty(x)) return false; }
return true;
}
Results under Node:
- first result:
return (Object.keys(obj).length === 0) - second result:
for (var x in obj) { return false; }... - third result:
for (var x in obj) { if (obj.hasOwnProperty(x)) return false; }... - forth result:
return ('{}' === JSON.stringify(obj))
Testing for Object with 0 keys 0.00018 0.000015 0.000015 0.000324
Testing for Object with 1 keys 0.000346 0.000458 0.000577 0.000657
Testing for Object with 2 keys 0.000375 0.00046 0.000565 0.000773
Testing for Object with 3 keys 0.000406 0.000476 0.000577 0.000904
Testing for Object with 4 keys 0.000435 0.000487 0.000589 0.001031
Testing for Object with 5 keys 0.000465 0.000501 0.000604 0.001148
Testing for Object with 6 keys 0.000492 0.000511 0.000618 0.001269
Testing for Object with 7 keys 0.000528 0.000527 0.000637 0.00138
Testing for Object with 8 keys 0.000565 0.000538 0.000647 0.00159
Testing for Object with 100 keys 0.003718 0.00243 0.002535 0.01381
Testing for Object with 1000 keys 0.0337 0.0193 0.0194 0.1337
Note that if your typical use case tests a non empty object with few keys, and rarely do you get to test empty objects or objects with 10 or more keys, consider the Object.keys(obj).length option. - otherwise go with the more generic (for... in...) implementation.
Note that Firefox seem to have a faster support for Object.keys(obj).length and Object.getOwnPropertyNames(obj).length, making it a better choice for any non empty Object, but still when it comes to empty objects, the (for...in...) is simply 10 times faster.
My 2 cents is that Object.keys(obj).length is a poor idea since it creates an object of keys just to count how many keys are inside, than destroys it! In order to create that object he needs to loop overt the keys... so why use it and not the (for... in...) option :)
var a = {};
function timeit(func,count) {
if (!count) count = 100000;
var start = Date.now();
for (i=0;i<count;i++) func();
var end = Date.now();
var duration = end - start;
console.log(duration/count)
}
function isEmpty1() {
return (Object.keys(a).length === 0)
}
function isEmpty2() {
for (x in a) { return false; }
return true;
}
function isEmpty3() {
for (x in a) { if (a.hasOwnProperty(x)) return false; }
return true;
}
function isEmpty4() {
return ('{}' === JSON.stringify(a))
}
for (var j=0;j<10;j++) {
a = {}
for (var i=0;i<j;i++) a[i] = i;
console.log('Testing for Object with '+Object.keys(a).length+' keys')
timeit(isEmpty1);
timeit(isEmpty2);
timeit(isEmpty3);
timeit(isEmpty4);
}
a = {}
for (var i=0;i<100;i++) a[i] = i;
console.log('Testing for Object with '+Object.keys(a).length+' keys')
timeit(isEmpty1);
timeit(isEmpty2);
timeit(isEmpty3);
timeit(isEmpty4, 10000);
a = {}
for (var i=0;i<1000;i++) a[i] = i;
console.log('Testing for Object with '+Object.keys(a).length+' keys')
timeit(isEmpty1,10000);
timeit(isEmpty2,10000);
timeit(isEmpty3,10000);
timeit(isEmpty4,10000);
Solution 6 - Javascript
Elegant way - use keys
var myEmptyObj = {};
var myFullObj = {"key":"value"};
console.log(Object.keys(myEmptyObj).length); //0
console.log(Object.keys(myFullObj).length); //1
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys
Solution 7 - Javascript
function isEmpty( o ) {
for ( var p in o ) {
if ( o.hasOwnProperty( p ) ) { return false; }
}
return true;
}
Solution 8 - Javascript
var x= {}
var y= {x:'hi'}
console.log(Object.keys(x).length===0)
console.log(Object.keys(y).length===0)
true
false
Solution 9 - Javascript
Surprised to see so many weak answers on such a basic JS question... The top answer is no good too for these reasons:
- it generates a global variable
- returns
trueonundefined - uses
for...inwhich is extremely slow by itself - function inside
for...inis useless - returnfalsewithouthasOwnPropertymagic will work fine
In fact there's a simpler solution:
function isEmpty(value) {
return Boolean(value && typeof value === 'object') && !Object.keys(value).length;
}
Solution 10 - Javascript
https://lodash.com/docs#isEmpty comes in pretty handy:
_.isEmpty({}) // true
_.isEmpty() // true
_.isEmpty(null) // true
_.isEmpty("") // true
Solution 11 - Javascript
How bad is this?
function(obj){
for(var key in obj){
return false; // not empty
}
return true; // empty
}
Solution 12 - Javascript
No need for a library.
function(){ //must be within a function
var obj = {}; //the object to test
for(var isNotEmpty in obj) //will loop through once if there is a property of some sort, then
return alert('not empty')//what ever you are trying to do once
return alert('empty'); //nope obj was empty do this instead;
}
Solution 13 - Javascript
It might be a bit hacky. You can try this.
if (JSON.stringify(data).length === 2) {
// Do something
}
Not sure if there is any disadvantage of this method.
Solution 14 - Javascript
fast onliner for 'dictionary'-objects:
function isEmptyDict(d){for (var k in d) return false; return true}
Solution 15 - Javascript
You can write a fallback if Array.isArray and Object.getOwnPropertyNames is not available
XX.isEmpty = function(a){
if(Array.isArray(a)){
return (a.length==0);
}
if(!a){
return true;
}
if(a instanceof Object){
if(a instanceof Date){
return false;
}
if(Object.getOwnPropertyNames(a).length == 0){
return true;
}
}
return false;
}
Solution 16 - Javascript
Imagine you have the objects below:
var obj1= {};
var obj2= {test: "test"};
Don't forget we can NOT use === sign for testing an object equality as they get inheritance, so If you using ECMA 5 and upper version of javascript, the answer is easy, you can use the function below:
function isEmpty(obj) {
//check if it's an Obj first
var isObj = obj !== null
&& typeof obj === 'object'
&& Object.prototype.toString.call(obj) === '[object Object]';
if (isObj) {
for (var o in obj) {
if (obj.hasOwnProperty(o)) {
return false;
break;
}
}
return true;
} else {
console.error("isEmpty function only accept an Object");
}
}
so the result as below:
isEmpty(obj1); //this returns true
isEmpty(obj2); //this returns false
isEmpty([]); // log in console: isEmpty function only accept an Object
Solution 17 - Javascript
funtion isEmpty(o,i)
{
for(i in o)
{
return!1
}
return!0
}
Solution 18 - Javascript
May be you can use this decision:
var isEmpty = function(obj) {
for (var key in obj)
if(obj.hasOwnProperty(key))
return false;
return true;
}
Solution 19 - Javascript
here's a good way to do it
function isEmpty(obj) {
if (Array.isArray(obj)) {
return obj.length === 0;
} else if (typeof obj === 'object') {
for (var i in obj) {
return false;
}
return true;
} else {
return !obj;
}
}
Solution 20 - Javascript
var hasOwnProperty = Object.prototype.hasOwnProperty;
function isArray(a) {
return Object.prototype.toString.call(a) === '[object Array]'
}
function isObject(a) {
return Object.prototype.toString.call(a) === '[object Object]'
}
function isEmpty(a) {
if (null == a || "" == a)return!0;
if ("number" == typeof a || "string" == typeof a)return!1;
var b = !0;
if (isArray(a)) {
if (!a.length)return!0;
for (var c = 0; c < a.length; c++)isEmpty(a[c]) || (b = !1);
return b
}
if (isObject(a)) {
for (var d in a)hasOwnProperty.call(a, d) && (isEmpty(a[d]) || (b = !1));
return b
}
return!0
}
Solution 21 - Javascript
I modified Sean Vieira's code to suit my needs. null and undefined don't count as object at all, and numbers, boolean values and empty strings return false.
'use strict';
// Speed up calls to hasOwnProperty
var hasOwnProperty = Object.prototype.hasOwnProperty;
var isObjectEmpty = function(obj) {
// null and undefined are not empty
if (obj == null) return false;
if(obj === false) return false;
if(obj === true) return false;
if(obj === "") return false;
if(typeof obj === "number") {
return false;
}
// Assume if it has a length property with a non-zero value
// that that property is correct.
if (obj.length > 0) return false;
if (obj.length === 0) return true;
// Otherwise, does it have any properties of its own?
// Note that this doesn't handle
// toString and valueOf enumeration bugs in IE < 9
for (var key in obj) {
if (hasOwnProperty.call(obj, key)) return false;
}
return true;
};
exports.isObjectEmpty = isObjectEmpty;
Solution 22 - Javascript
here my solution
function isEmpty(value) {
if(Object.prototype.toString.call(value) === '[object Array]') {
return value.length == 0;
} else if(value != null && typeof value === 'object') {
return Object.getOwnPropertyNames(value).length == 0;
} else {
return !(value || (value === 0));
}
}
Chears
Solution 23 - Javascript
if (Object.getOwnPropertyNames(obj1).length > 0)
{
alert('obj1 is empty!');
}