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Showing content from http://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/toString below:

Symbol.prototype.toString() - JavaScript | MDN

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The toString() method of Symbol values returns a string representing this symbol value.

console.log(Symbol("desc").toString());
// Expected output: "Symbol(desc)"

console.log(Symbol.iterator.toString());
// Expected output: "Symbol(Symbol.iterator)

console.log(Symbol.for("foo").toString());
// Expected output: "Symbol(foo)"

// console.log(Symbol('foo') + 'bar');
// Expected output: Error: Can't convert symbol to string

None.

A string representing the specified symbol value.

The Symbol object overrides the toString method of Object; it does not inherit Object.prototype.toString(). For Symbol values, the toString method returns a descriptive string in the form "Symbol(description)", where description is the symbol's description.

The toString() method requires its this value to be a Symbol primitive or wrapper object. It throws a TypeError for other this values without attempting to coerce them to symbol values.

Because Symbol has a [Symbol.toPrimitive]() method, that method always takes priority over toString() when a Symbol object is coerced to a string. However, because Symbol.prototype[Symbol.toPrimitive]() returns a symbol primitive, and symbol primitives throw a TypeError when implicitly converted to a string, the toString() method is never implicitly called by the language. To stringify a symbol, you must explicitly call its toString() method or use the String() function.

Symbol("desc").toString(); // "Symbol(desc)"

// well-known symbols
Symbol.iterator.toString(); // "Symbol(Symbol.iterator)"

// global symbols
Symbol.for("foo").toString(); // "Symbol(foo)"

The only way to make JavaScript implicitly call toString() instead of [Symbol.toPrimitive]() on a symbol wrapper object is by deleting the [Symbol.toPrimitive]() method first.

Warning: You should not do this in practice. Never mutate built-in objects unless you know exactly what you're doing.

delete Symbol.prototype[Symbol.toPrimitive];
console.log(`${Object(Symbol("foo"))}`); // "Symbol(foo)"

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