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 |
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"
.
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"
Specification | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Symbol.toPrimitive' in that specification. | Standard | Initial definition. |
ECMAScript 2017 Draft (ECMA-262) The definition of 'Symbol.toPrimitive' in that specification. | Draft |
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | 48 | 44 (44) | ? | ? | ? |
Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|
Basic support | ? | ? | 44.0 (44) | ? | ? | ? |
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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/toPrimitive