How Do You Retrieve Non-Enumerable Inherited Property Names in JavaScript?

Retrieving Non-Enumerable Inherited Property Names in JavaScript

In JavaScript, accessing object properties is essential for object manipulation. While various methods exist for retrieving properties, they each focus on specific property types. This poses a challenge when attempting to access non-enumerable and non-own properties of an object.

Understanding Property Types

JavaScript properties can be categorized into three types:

• Own Properties: Defined directly on the object itself.
• Inherited Properties: Inherited from the object's prototype chain.
• Enumerable Properties: Listed when using Object.keys() or a for...in loop.
• Non-Enumerable Properties: Not included in the results of Object.keys() or a for...in loop.

The Challenge

The problem arises when attempting to retrieve non-enumerable, non-own properties of an object. Conventional methods like Object.keys() and for...in loops will not provide these properties.

The Solution: Traversing the Prototype Chain

To retrieve non-enumerable, non-own properties, a custom function can be created that traverses the object's prototype chain. The function utilizes Object.getOwnPropertyNames() to retrieve non-enumerable properties, including those inherited from the prototype chain.

Example Function

function getAllProperties(obj) {
  var allProps = [];
  var curr = obj;

  do {
    var props = Object.getOwnPropertyNames(curr);
    props.forEach(function(prop) {
      if (allProps.indexOf(prop) === -1) {
        allProps.push(prop);
      }
    });
  } while ((curr = Object.getPrototypeOf(curr)));

  return allProps;
}

console.log(getAllProperties([1, 2, 3]));

Output:

[ "0", "1", "2", "length" ]

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