How to Customize Equality for JavaScript Set Objects?

Customizing Object Equality for JavaScript Set

The recently introduced ES6 Set object utilizes an identity algorithm for equality comparisons, similar to the operator. This approach is not well-suited for comparing objects, as demonstrated in the following example:

var set = new Set();
set.add({a:1});
set.add({a:1});
console.log([...set.values()]); // Array [ Object, Object ]

Two objects with identical properties are considered distinct elements within the Set because they are not the same exact object. This limitation raises the question of how to customize equality for Set objects to facilitate deep object comparisons.

Current Limitations and Proposed Solutions

As of now, the ES6 Set object lacks built-in methods for customizing equality comparisons. To address this, the author suggests creating a derived object that inherits from Set and overrides the .has(), .add(), and .delete() methods to perform deep object comparisons. However, this approach is inefficient as it does not utilize the underlying Set object's functionality.

The article references a proposal in development that aims to introduce Records and Tuples into JavaScript. These immutable data structures are expected to implement deep value comparison, which would effectively solve the problem described. However, this proposal is still under development and not yet fully implemented.

Other Considerations

Some alternative strategies for object comparison within Sets include:

• Custom Wrapper Objects: Create wrapper objects that implement deep object comparison and store these wrappers in the Set.
• Custom Equality Function: Define a custom equality function and use it as the criteria for the Set's has() method.

These approaches provide workarounds but do not directly customize the Set object's equality behavior.

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