mongez-supportive-is-misc

To check if an object is a Promise or Date in JavaScript, you use object-kind predicates like isPromise and isDate. These predicates identify object instances by their constructor-name semantics, providing precise type detection across cross-environment code.

The isDate predicate returns true for invalid dates because it checks the object-kind constructor-name semantics rather than the date's value validity. This means an invalid Date instance is still recognized as a Date object, a known quirk developers must handle when validating JavaScript date values.

To detect FormData and FormElement objects, you use the isFormData and isFormElement predicates. These checks rely on DOM globals, meaning they function specifically within web environments where DOM APIs are available for identifying form-related object instances.

The best way to identify a Generator object in JavaScript is using the isGenerator predicate. This check is duck-typed, meaning it identifies generators by their structural shape and behavior rather than relying solely on constructor names, avoiding cross-environment prototype issues.

Supportive-is type predicates are designed for cross-environment behavior, but they have edge cases. For example, isFormElement and isFormData rely on DOM globals, so they will not work in pure Node.js environments lacking browser APIs.

To use supportive-is predicates in a TypeScript project, import the specific functions like isPromise or isDate. Apply them as type guards to narrow object types, leveraging constructor-name semantics to accurately validate instances and handle edge cases like invalid dates.