An Interest In:
Web News this Week
- April 26, 2024
- April 25, 2024
- April 24, 2024
- April 23, 2024
- April 22, 2024
- April 21, 2024
- April 20, 2024
How to Check if Object is Empty in JavaScript
Here's a Code Recipe to check if an object is empty or not. For newer browsers, you can use plain vanilla JS and use the new "Object.keys" But for older browser support, you can install the Lodash library and use their "isEmpty" method
const empty = {};/* ------------------------- Plain JS for Newer Browser----------------------------*/Object.keys(empty).length === 0 && empty.constructor === Object// true/* ------------------------- Lodash for Older Browser----------------------------*/_.isEmpty(empty)// true
What is Vanilla JavaScript
Vanilla JavaScript is not a new framework or library. It's just regular, plain JavaScript without the use of a library like Lodash or jQuery.
A. Empty Object Check in Newer Browsers
We can use the built-in Object.keys
method to check for an empty object.
const empty = {};Object.keys(empty).length === 0 && empty.constructor === Object;
Why do we need an additional constructor
check?
You may be wondering why do we need the constructor
check. Well, it's to cover for the wrapper instances. In JavaScript, we have 9 built-in constructors.
new Object();new String();new Number();new Boolean();new Array();new RegExp();new Function();new Date();
So we can create an empty object with new Object()
. Side note: you should NEVER create an object using the constructor. It's considered bad practice, see Airbnb Style Guide and ESLint.
const obj = new Object();Object.keys(obj).length === 0; // true
So just using the Object.keys
, it does return true
when the object is empty . But what happens when we create a new object instance using these other constructors.
function badEmptyCheck(value) { return Object.keys(value).length === 0;}badEmptyCheck(new String()); // true badEmptyCheck(new Number()); // true badEmptyCheck(new Boolean()); // true badEmptyCheck(new Array()); // true badEmptyCheck(new RegExp()); // true badEmptyCheck(new Function()); // true badEmptyCheck(new Date()); // true
Ah ya ya, we have a false positive
Solving false positive with constructor
check
Let's correct this by adding a constructor check.
function goodEmptyCheck(value) { Object.keys(value).length === 0 && value.constructor === Object; // constructor check}goodEmptyCheck(new String()); // false goodEmptyCheck(new Number()); // false goodEmptyCheck(new Boolean()); // false goodEmptyCheck(new Array()); // false goodEmptyCheck(new RegExp()); // false goodEmptyCheck(new Function()); // false goodEmptyCheck(new Date()); // false
Beautiful! We have covered our edge case
Testing empty check on other values
Alright, let's test our method on some values and see what we get
function isEmptyObject(value) { return Object.keys(value).length === 0 && value.constructor === Object;}
Looks good so far, it returns false
for non-objects.
isEmptyObject(100) // falseisEmptyObject(true) // falseisEmptyObject([]) // false
But watch out! These values will throw an error.
// TypeError: Cannot covert undefined or null ot objectgoodEmptyCheck(undefined)goodEmptyCheck(null)
Improve empty check for null
and undefined
If you don't want it to throw a TypeError
, you can add an extra check:
let value;value // null and undefined check && Object.keys(value).length === 0 && value.constructor === Object;value = null; // nullvalue = undefined; // undefined
Perfect, no error is thrown
B. Empty Object Check in Older Browsers
What if you need to support older browsers? Heck, who am I kidding! We all know when I say older browsers, I'm referring to Internet Explorer Well, we have 2 options. We can stick with vanilla or utilize a library.
Checking empty object with JavaScript
The plain vanilla way is not as concise. But it does do the job
function isObjectEmpty(value) { return Object.prototype.toString.call(value) === "[object Object]" && JSON.stringify(value) === "{}"}
It returns true
for objects.
isObjectEmpty({}); // true isObjectEmpty(new Object()); // true
Excellent, it doesn't get trick by our constructor objects
isObjectEmpty(new String()); // false isObjectEmpty(new Number()); // false isObjectEmpty(new Boolean()); // false isObjectEmpty(new Array()); // false isObjectEmpty(new RegExp()); // false isObjectEmpty(new Function()); // false isObjectEmpty(new Date()); // false
And we're covered for null
and undefined
. It will return false
and not throw a TypeError
.
isObjectEmpty(null); // falseisObjectEmpty(undefined); // false
Checking empty object with external libraries
There are tons of external libraries you can use to check for empty objects. And most of them have great support for older browsers
Lodash
_.isEmpty({});// true
Underscore
_.isEmpty({});// true
jQuery
jQuery.isEmptyObject({});// true
Vanilla vs Libraries
The answer is it depends! I'm a huge fan of going vanilla whenever possible as I don't like the overhead of an external library. Plus for smaller apps, I'm too lazy to set up the external library . But if your app already has an external library installed, then go ahead and use it. You will know your app better than anyone else. So choose what works best for your situation
Conscious Decision Making
- @lexLohr: Like most things in development, it's a compromise. A good developer is aware of the available options. A great developer is also aware of their implications.
I love this mindset so much! Often, we have to make some compromises. And there's nothing wrong with that. Especially, when you work within a team, sometimes disagreement arises. But in the end, we have to make a decision. This doesn't mean we blind ourselves from other options. Quite the opposite, we do our best to seek other possible solutions and understand each implication. That's how we can make an informed decision. Maybe compromise is not the right word, I think of it as "conscious decision making"
Yup, I too can coin terms, just like Gwyneth Paltrow's conscious uncoupling. Maybe I should start a tech version of Goop...but minus the jade roller and the other "interesting" products
Community Input
for (var key in object) { if (object.hasOwnProperty(key)) { return false }}return true
Object.prototype.toString.call(a) == "[object Object]" && JSON.stringify(a) == "{}"
@kevinsar: Lodash tends to throw security exceptions in analysis tools like sonarqube and whitesource, I tend to just create my own util function and use vanilla instead.
- @sush_keny: (Because of) prototype pollution
Resources
- MDN: Object.keys()
- w3schools: Built-in JavaScript Constructors
- Stack Overflow: Is object empty?
- Stack Overflow: How do I test for an empty JavaScript object?
- CSS Tricks: Understanding JavaScript Constructors
- JavaScript's Primitive Wrapper Objects
- Wrapper Objects
- JavaScripts Primitive Wrapper Objects
- ESLint: Disallow Primitive Wrapper Instances
- Airbnb: no-new-object
- Lodash: isEmpty
- Underscore: isEmpty
- jQuery: isEmptyObject
Thanks for reading
To find more code tidbits, please visit samanthaming.com
Original Link: https://dev.to/samanthaming/how-to-check-if-object-is-empty-in-javascript-2m9
Dev To
An online community for sharing and discovering great ideas, having debates, and making friendsMore About this Source Visit Dev To