Is object empty? [duplicate]

Question

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; } 

Answer 1

For ECMAScript5 (not supported in all browsers yet though), you can use:

Object.keys(obj).length === 0 

Answer 2

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.