How to check if object has any properties in JavaScript?

Deep-diving: alternative approaches

Handling non-enumerable properties

To account for non-enumerable properties, use Object.getOwnPropertyNames(obj).length. It's like Object.keys on steroids.

Example:

const hasNonEnumerable = Object.getOwnPropertyNames({prop: 'value'}).length > 0; // true. You can't hide from getOwnPropertyNames!
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Checking specific properties

To confirm the existence of a specific property in an object without involving the prototype chain, put hasOwnProperty() to work.

Example:

const object = { ownProp: 'exists' };
const hasOwn = object.hasOwnProperty('ownProp'); // true. Property found? Achievement unlocked!
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Counting user-defined properties only

If interested in user-defined properties alone, a for...in loop accompanied by hasOwnProperty() is your weapon of choice.

Example:

let userDefinedPropertyCount = 0;
const object = { foo: 'bar', baz: 'qux' };
for (let key in object) {
  if (object.hasOwnProperty(key)) {
    userDefinedPropertyCount++; // Increments faster than my social media followers... 
  }
}
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Leveraging libraries

For jQuery aficionados, $.isEmptyObject(obj) offers a consistently 'jQuery-esque' approach.

Example:

const isEmpty = $.isEmptyObject({}); // true. jQuery not just for DOM manipulation!
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In an ES5 environment, consider shims to bolster older browser support for methods like Object.keys.

Nitty-gritty details

Grasping the prototype chain

To distinguish between inherited properties and user-defined properties, get to grips with the prototype chain.

Example:

const base = { inheritedProp: 'inherited' };
const obj = Object.create(base);
obj.ownProp = 'own';
// 'inheritedProp' is inherited, 'ownProp' is user-defined. It's a family thing!
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Controlling property visibility

You can decide which properties are enumerated by Object.defineProperty, controlling their enumerability.

Example:

const object = {};
Object.defineProperty(object, 'hidden', {
  value: 'secret', 
  enumerable: false,
});
// 'hidden' won't be counted by Object.keys(). More elusive than my diet plan...
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Sidestepping issues

Keep an eye out for edge cases, like objects with inherited non-enumerable properties, which might sneak past your property count.

Streamlining patterns

Encapsulate enumeration logic in a utility function for repeated checks. Efficiency, thy name is isObjectEmpty()!

Example:

function isObjectEmpty(obj) {
  return Object.keys(obj).length === 0;
}
// Pretty handy function, huh? 
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