Symbol.prototype.toString()
The toString()
method returns a string representing the specified symbol value.
Try it
Syntax
js
toString()
Return value
A string representing the specified symbol value.
Description
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 [@@toPrimitive]()
method, that method always takes priority over toString()
when a Symbol
object is coerced to a string. However, because Symbol.prototype[@@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.
Examples
Using toString()
js
Symbol("desc").toString(); // "Symbol(desc)"
// well-known symbols
Symbol.iterator.toString(); // "Symbol(Symbol.iterator)"
// global symbols
Symbol.for("foo").toString(); // "Symbol(foo)"
Implicitly calling toString()
The only way to make JavaScript implicitly call toString()
instead of [@@toPrimitive]()
on a symbol wrapper object is by deleting the @@toPrimitive
method first.
Warning: You should not do this in practice. Never mutate built-in objects unless you know exactly what you're doing.
js
delete Symbol.prototype[Symbol.toPrimitive];
console.log(`${Object(Symbol("foo"))}`); // "Symbol(foo)"
Specifications
Specification |
---|
ECMAScript Language Specification # sec-symbol.prototype.tostring |
Browser compatibility
BCD tables only load in the browser