Has instance symbol.
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> Has instance [symbol][mdn-symbol] which is used to determine if a constructor object recognizes an object as its instance.
``bash`
npm install @stdlib/symbol-has-instance
`javascript`
var HasInstanceSymbol = require( '@stdlib/symbol-has-instance' );
#### HasInstanceSymbol
Has instance [symbol][mdn-symbol] which is used to determine if a constructor object recognizes an object as its instance.
`javascript`
var s = typeof HasInstanceSymbol;
// e.g., returns 'symbol'
- The [symbol][mdn-symbol] is only supported in environments which support [symbols][mdn-symbol]. In non-supporting environments, the value is null.
- The instanceof operator uses the following algorithm to determine the return value of object instanceof constructor:
- If constructor has a [HasInstanceSymbol]() method, the instanceof operator calls the method with object as the first argument and returns the result (coerced to a boolean). If constructor is not an object or if constructor[HasInstanceSymbol] is neither null, undefined, nor a function, the instanceof operator raises an exception.constructor
- Otherwise, if does not have a [HasInstanceSymbol]() method (i.e., constructor[HasInstanceSymbol] is null or undefined), the instanceof operator determines the result using the same algorithm as Function.prototype[HasInstanceSymbol](). If constructor is not a function, the instanceof operator raises an exception.
`javascript
var isArray = require( '@stdlib/assert-is-array' );
var instanceOf = require( '@stdlib/assert-instance-of' );
var defineProperty = require( '@stdlib/utils-define-property' );
var HasInstanceSymbol = require( '@stdlib/symbol-has-instance' );
function ArrayLike() {
return {
'length': 3,
'0': 4,
'1': 5,
'2': 6
};
}
function hasInstance( instance ) {
return isArray( instance );
}
var x = [ 1, 2, 3 ];
defineProperty( ArrayLike, HasInstanceSymbol, {
'configurable': true,
'value': null
});
console.log( instanceOf( x, ArrayLike ) );
defineProperty( ArrayLike, HasInstanceSymbol, {
'configurable': true,
'value': hasInstance
});
console.log( instanceOf( x, ArrayLike ) );
`
*
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For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].
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---
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Copyright © 2016-2026. The Stdlib [Authors][stdlib-authors].
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[umd]: https://github.com/umdjs/umd
[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules
[deno-url]: https://github.com/stdlib-js/symbol-has-instance/tree/deno
[deno-readme]: https://github.com/stdlib-js/symbol-has-instance/blob/deno/README.md
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[branches-url]: https://github.com/stdlib-js/symbol-has-instance/blob/main/branches.md
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[mdn-symbol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol