What is the Lisp's symbol equivalent of JavaScript?

In JavaScript, the closest equivalent to Lisp’s symbols are actually symbols themselves, introduced in ES6. JavaScript’s Symbol type represents unique, immutable identifiers. They can be used as keys for object properties, ensuring no accidental name conflicts with other property names, but they aren’t exactly like Lisp symbols in terms of variable references.

Here’s a breakdown of how Symbol in JavaScript compares to Lisp symbols and what it can and can’t do:

Uniqueness and Identity:
In JavaScript, each Symbol created is unique, which aligns with how Lisp symbols can serve as unique identifiers. For example:

const sym1 = Symbol("mySymbol");
const sym2 = Symbol("mySymbol");
console.log(sym1 === sym2); // false

Even if two symbols have the same description, they are unique.

No Direct Reference to Variables:
Lisp symbols can refer to variable names or functions in the global environment. JavaScript symbols, however, don’t directly link to variables or hold references to values. They are more like keys that don’t collide with other keys. This means you can’t use Symbol to refer to a variable in the same way a Lisp symbol can refer to a binding.

Usage as Object Keys:
JavaScript Symbols are often used as property keys in objects to create “hidden” properties that don’t interfere with other keys. Here’s how you might use them:

const key = Symbol("secretKey");
const obj = {
    [key]: "hidden value"
};
console.log(obj[key]); // "hidden value"

Workarounds for Variable Reference Behavior
If you want something closer to Lisp-like behavior (e.g., symbolic names that refer to variables), you might use string keys in a map or even an object with property names that hold variable values. For example:

const symbols = {
   myVariable: 42,
   anotherVariable: "hello"
};

const symbolName = "myVariable";
console.log(symbols[symbolName]); // 42

This won’t give you true symbolic manipulation, but it allows you to indirectly reference variables by their names.

In summary:

JavaScript Symbol provides unique identifiers, useful for keys in objects but without the variable-binding references Lisp offers.
You can simulate references with object properties or a map, though this approach lacks Lisp’s symbolic manipulation capabilities.