在此页

• 描述
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

Symbol.toPrimitive is a symbol that specifies a function valued property that is called to convert an object to a corresponding primitive value.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

描述

With the help of the Symbol.toPrimitive property (used as a function value), an object can be converted to a primitive value. The function is called with a string argument hint , which specifies the preferred type of the result primitive value. The hint argument can be one of " number " , " string " ，和 " default " .

特性属性在 Symbol.toPrimitive
可写	no
可枚举	no
可配置	no

范例

Modifying primitive values converted from an object

Following example describes how Symbol.toPrimitive property can modify the primitive value converted from an object.

// An object without Symbol.toPrimitive property.
var obj1 = {};
console.log(+obj1);     // NaN
console.log(`${obj1}`); // "[object Object]"
console.log(obj1 + ''); // "[object Object]"
// An object with Symbol.toPrimitive property.
var obj2 = {
  [Symbol.toPrimitive](hint) {
    if (hint == 'number') {
      return 10;
    }
    if (hint == 'string') {
      return 'hello';
    }
    return true;
  }
};
console.log(+obj2);     // 10        -- hint is "number"
console.log(`${obj2}`); // "hello"   -- hint is "string"
console.log(obj2 + ''); // "true"    -- hint is "default"
					

规范

规范
ECMAScript (ECMA-262) The definition of 'Symbol.toPrimitive' in that specification.

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
toPrimitive	Chrome 47	Edge 15	Firefox 44	IE No	Opera 34	Safari 10	WebView Android 47	Chrome Android 47	Firefox Android 44	Opera Android 34	Safari iOS 10	Samsung Internet Android 5.0	nodejs 6.0.0

图例

完整支持

完整支持

不支持

不支持

另请参阅

• Date.prototype[@@toPrimitive]
• Symbol.prototype[@@toPrimitive]
• Object.prototype.toString()
• Object.prototype.valueOf()

元数据

• 最后修改： May 7, 2020

相关话题

1. 标准内置对象
2. Symbol
3. 特性
   1. Symbol.asyncIterator
   2. Symbol.hasInstance
   3. Symbol.isConcatSpreadable
   4. Symbol.iterator
   5. Symbol.match
   6. Symbol.matchAll
   7. Symbol.prototype.description
   8. Symbol.replace
   9. Symbol.search
   10. Symbol.species
   11. Symbol.split
   12. Symbol.toPrimitive
   13. Symbol.toStringTag
   14. Symbol.unscopables
4. 方法
   1. Symbol.for()
   2. Symbol.keyFor()
   3. Symbol.prototype.toSource()
   4. Symbol.prototype.toString()
   5. Symbol.prototype.valueOf()
   6. Symbol.prototype[@@toPrimitive]
5. 继承：
6. Function
7. 特性
   1. Function.arguments
   2. Function.caller
   3. Function.displayName
   4. Function.length
   5. Function.name
8. 方法
   1. Function.prototype.apply()
   2. Function.prototype.bind()
   3. Function.prototype.call()
   4. Function.prototype.toSource()
   5. Function.prototype.toString()
9. Object
10. 特性
    1. Object.prototype.__proto__
    2. Object.prototype.constructor
11. 方法
    1. Object.prototype.__defineGetter__()
    2. Object.prototype.__defineSetter__()
    3. Object.prototype.__lookupGetter__()
    4. Object.prototype.__lookupSetter__()
    5. Object.prototype.hasOwnProperty()
    6. Object.prototype.isPrototypeOf()
    7. Object.prototype.propertyIsEnumerable()
    8. Object.prototype.toLocaleString()
    9. Object.prototype.toSource()
    10. Object.prototype.toString()
    11. Object.prototype.valueOf()
    12. Object.setPrototypeOf()