Checking for Empty JavaScript Objects
When working with JavaScript, you may encounter scenarios where your application returns an empty object, denoted as { }. Determining the emptiness of an object is essential for proper data handling. This article explores several methods to test for empty JavaScript objects.
Method 1: for...in Loop and Object.hasOwn (ECMA 2022)
This method utilizes a for...in loop to iterate over an object's properties. If any own properties exist, it indicates that the object is not empty, returning false. Otherwise, it returns true.
function isEmpty(obj) { for (const prop in obj) { if (Object.hasOwn(obj, prop)) { return false; } } return true; }
Method 2: Object.keys and length
While straightforward, this approach is less efficient as it creates an array of all property names, which has a complexity of O(N).
function isEmpty(obj) { return Object.keys(obj).length === 0; }
Method 3: Type Checks for { }-like Objects
To differentiate between empty objects ({ }) and other objects with no own properties (e.g., Dates), type checks are necessary:
function isEmptyObject(value) { if (value == null) { return false; // null or undefined } if (typeof value !== 'object') { return false; // boolean, number, string, function, etc. } const proto = Object.getPrototypeOf(value); if (proto !== null && proto !== Object.prototype) { return false; // `Object.create(null)` or other objects with custom prototypes } return isEmpty(value); // check for any own properties }
Method 4: Using Third-Party Libraries
Many popular JavaScript libraries provide functions for checking empty objects, such as:
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