Web/JavaScript/Reference/Global objects/Symbol/toPrimitive

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

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".

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

Examples

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"

Specifications

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

Browser compatibility

Update compatibility data on GitHub

	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 Full support 47	Edge Full support 15	Firefox Full support 44	IE No support No	Opera Full support 34	Safari Full support 10	WebView Android Full support 47	Chrome Android Full support 47	Firefox Android Full support 44	Opera Android Full support 34	Safari iOS Full support 10	Samsung Internet Android Full support 5.0	nodejs Full support 6.0.0

Legend

Full support: Full support
No support: No support