Symbol.toStringTag

该Symbol.toStringTag公知的符号是在创建对象的默认字符串描述中使用的字符串值属性。它由该Object.prototype.toString()方法在内部访问。

| Symbol.toStringTag 属性的属性特性：|

|:----|

| Writable | no |

| Enumerable | no |

| Configurable | no |

描述

许多内置的 JavaScript 对象类型即便没有toStringTag属性，也能被toString() 方法识别并返回特定的类型标签，比如：

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

其他的有一个内置的toStringTag符号定义：

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

在创建自己的类时，JavaScript默认为“Object”标签：

class ValidatorClass {}

Object.prototype.toString.call(new ValidatorClass() // "[object Object]"

现在，在toStringTag您的帮助下，您可以设置自己的自定义标签：

class ValidatorClass {
  get [Symbol.toStringTag]() {
    return 'Validator';
  }
}

Object.prototype.toString.call(new ValidatorClass() // "[object Validator]"

规范

Specification	Status	Comment
ECMAScript 2015 (6th Edition, ECMA-262)The definition of 'Symbol.toStringTag' in that specification.	Standard	Initial definition.
ECMAScript Latest Draft (ECMA-262)The definition of 'Symbol.toStringTag' in that specification.	Draft

浏览器兼容性

Feature	Chrome	Edge	Firefox (Gecko)	Internet Explorer	Opera	Safari
Basic support	49	(Yes)	51 (51)	No support	?	?

Feature	Android	Chrome for Android	Edge	Firefox Mobile (Gecko)	IE Mobile	Opera Mobile	Safari Mobile
Basic support	?	?	(Yes)	51.0 (51)	No support	?	?