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 Language Specification # sec-symbol.toprimitive |
Browser compatibility
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