Date.prototype[Symbol.toPrimitive]()

Try it

// Depending on timezone, your results will vary
const date = new Date("20 December 2019 14:48");

console.log(date[Symbol.toPrimitive]("string"));
// Expected output: "Fri Dec 20 2019 14:48:00 GMT+0530 (India Standard Time)"

console.log(date[Symbol.toPrimitive]("number"));
// Expected output: 1576833480000

Syntax

date[Symbol.toPrimitive](hint)

Parameters

hint

A string representing the type of the primitive value to return. The following values are valid:

• "string" or "default": The method should return a string.
• "number": The method should return a number.

Return value

If hint is "string" or "default", this method returns a string by coercing the this value to a string (first trying toString() then trying valueOf()).

If hint is "number", this method returns a number by coercing the this value to a number (first trying valueOf() then trying toString()).

Exceptions

TypeError

Thrown if the hint argument is not one of the three valid values.

Description

The [Symbol.toPrimitive]() method is part of the type coercion protocol. JavaScript always calls the [Symbol.toPrimitive]() method in priority to convert an object to a primitive value. You rarely need to invoke the [Symbol.toPrimitive]() method yourself; JavaScript automatically invokes it when encountering an object where a primitive value is expected.

The [Symbol.toPrimitive]() method of the Date object returns a primitive value by either invoking this.valueOf() and returning a number, or invoking this.toString() and returning a string. It exists to override the default primitive coercion process to return a string instead of a number, because primitive coercion, by default, calls valueOf() before toString(). With the custom [Symbol.toPrimitive](), new Date(0) + 1 returns "Thu Jan 01 1970 00:00:00 GMT+0000 (Coordinated Universal Time)1" (a string) instead of 1 (a number).

Examples

Using [Symbol.toPrimitive]()

const d = new Date(0); // 1970-01-01T00:00:00.000Z

d[Symbol.toPrimitive]("string"); // "Thu Jan 01 1970 00:00:00 GMT+0000 (Coordinated Universal Time)"
d[Symbol.toPrimitive]("number"); // 0
d[Symbol.toPrimitive]("default"); // "Thu Jan 01 1970 00:00:00 GMT+0000 (Coordinated Universal Time)"

Specifications

Browser compatibility

See also

• Symbol.toPrimitive