The Symbol.toStringTag
well-known symbol is a string valued property that is used in the creation of the default string description of an object. It is accessed internally by the Object.prototype.toString()
method.
Symbol.toStringTag
Try it
Property attributes of Symbol.toStringTag |
|
---|---|
Writable | no |
Enumerable | no |
Configurable | no |
Examples
Default tags
Object.prototype.toString.call('foo'); // "[object String]" Object.prototype.toString.call([1, 2]); // "[object Array]" Object.prototype.toString.call(3); // "[object Number]" Object.prototype.toString.call(true); // "[object Boolean]" Object.prototype.toString.call(undefined); // "[object Undefined]" Object.prototype.toString.call(null); // "[object Null]" // ... and more
Built-in toStringTag symbols
Object.prototype.toString.call(new Map()); // "[object Map]" Object.prototype.toString.call(function* () {}); // "[object GeneratorFunction]" Object.prototype.toString.call(Promise.resolve()); // "[object Promise]" // ... and more
Custom classes default to object tag
When creating your own class, JavaScript defaults to the "Object" tag:
class ValidatorClass {} Object.prototype.toString.call(new ValidatorClass()); // "[object Object]"
Custom tag with toStringTag
Now, with the help of toStringTag
, you are able to set your own custom tag:
class ValidatorClass { get [Symbol.toStringTag]() { return 'Validator'; } } Object.prototype.toString.call(new ValidatorClass()); // "[object Validator]"
toStringTag available on all DOM prototype objects
Due to a WebIDL spec change in mid-2020, browsers are adding a Symbol.toStringTag
property to all DOM prototype objects. For example, to access the Symbol.toStringTag
property on HTMLButtonElement
:
let test = document.createElement('button'); test.toString(); // Returns [object HTMLButtonElement] test[Symbol.toStringTag]; // Returns HTMLButtonElement
Specifications
Browser compatibility
Desktop | Mobile | Server | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | Deno | Node.js | |
toStringTag |
49
|
15
|
51
|
No
|
36
|
10
|
49
|
49
|
51
|
36
|
10
|
5.0
|
1.0
|
6.0.0
4.0.0
|
dom_objects |
50
|
79
|
78
|
No
|
37
|
14
|
50
|
50
|
79
|
37
|
14
|
5.0
|
1.0
|
No
|
See also
© 2005–2022 MDN contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/toStringTag