ToPrimitiveSymbol

Symbol which specifies a method for converting an object to a primitive value.

Installation

npm install @stdlib/symbol-to-primitive

Usage

var ToPrimitiveSymbol = require( '@stdlib/symbol-to-primitive' );

ToPrimitiveSymbol

Symbol which specifies a method for converting an object to a primitive value.

var s = typeof ToPrimitiveSymbol;
// e.g., returns 'symbol'

Notes

• The symbol is only supported in environments which support symbols. In non-supporting environments, the value is null.

• When an object needs to be converted to a primitive value, JavaScript runtimes look for a [ToPrimitiveSymbol]() method on the object. If the method exists, JavaScript runtimes call the method with a hint string argument (one of 'number', 'string', or 'default') indicating the preferred type of the primitive value to be returned.

  • If the hint is 'number', the method should return a number.
  • If the hint is 'string', the method should return a string.
  • If the hint is 'default', the method can return either a number or a string.

• If an object does not have a [ToPrimitiveSymbol]() method, JavaScript runtimes use the default type conversion algorithm by calling valueOf() and/or toString() methods.

Examples

var defineProperty = require( '@stdlib/utils-define-property' );
var Number = require( '@stdlib/number-ctor' );
var ToPrimitiveSymbol = require( '@stdlib/symbol-to-primitive' );

function CustomObject( value ) {
    if ( !(this instanceof CustomObject) ) {
        return new CustomObject( value );
    }
    this._value = value;
    return this;
}

function toPrimitive( hint ) {
    var value = this._value;
    if ( hint === 'string' ) {
        return 'CustomObject: ' + value;
    }
    if ( hint === 'number' ) {
        return value;
    }
    // Default hint:
    return value;
}

defineProperty( CustomObject.prototype, ToPrimitiveSymbol, {
    'configurable': false,
    'enumerable': false,
    'writable': false,
    'value': toPrimitive
});

var obj = new CustomObject( 42 );

console.log( String( obj ) );
// => 'CustomObject: 42'

console.log( Number( obj ) );
// => 42

console.log( obj + 10 );
// => 52

Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

Community

License

See LICENSE.

Copyright

Copyright © 2016-2026. The Stdlib Authors.