Delving into the World of ES6 Symbols

Throughout my experience with various programming languages, from C# to Lisp to Scala to Haskell, symbols have consistently behaved as singleton objects. This means that any two symbols with the same name are guaranteed to be identical.

In Racket: (equal? 'foo 'foo) returns true

In Common Lisp: (eq 'foo 'foo) returns true

In Ruby: :foo == :foo returns true

In Scala: 'foo == 'foo returns true

In ECMAScript 6: Symbol('foo') === Symbol('foo') returns false

The advantage of symbols being singletons is clear: they can be used in maps/dictionaries without the risk of the key not being equal to the input due to changes in hashing algorithms (like in Ruby).

However, why does ECMAScript 6 take a different approach and how can this be worked around?

javascriptecmascript-6symbols

Answer №1

To achieve a similar effect of symbols being easily recognizable by name, you can utilize registered global symbols:

var symbol1 = Symbol.for("bar");
var symbol2 = Symbol.for("bar");
symbol1 === symbol2; // true

In addition to using global symbols, you also have the option to create your own Symbol registry using either a Map instance or a plain object.

Update: In creating a new Symbol instance with an optional string parameter, the intention is to provide a means for identifying the significance and purpose of a symbol to the developer. This description string helps convey information about the symbol without compromising its uniqueness as a key value.

Furthermore, if needed, you can compare the result of calling .toString() on two similarly constructed Symbol instances. While this practice may be considered questionable, it is technically possible.

Additional update: The default behavior of Symbol creation in JavaScript makes this data type more valuable compared to other languages like Erlang's atoms or Clojure keys. By providing a unique guaranteed value by default, JavaScript effectively solves the issue of namespace collisions. Despite still allowing for "well-known" symbols, having unique values readily available without concerns of conflicts with other code is advantageous. JavaScript faces the challenge of a global namespace that can be influenced by external factors, making it crucial for developers to prioritize avoiding unintentional clashes in their code.

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