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

Property attributes of Symbol.toPrimitive
Writable no
Enumerable no
Configurable no

Description

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", and "default".

Examples

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"

Specifications

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

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support48 Yes44 No Yes Yes
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidIE mobileOpera AndroidiOS Safari
Basic support Yes Yes Yes44 No Yes Yes

See also

Document Tags and Contributors

 Last updated by: Delapouite,