NullableUndefineableJSAnyExtension

extension NullableUndefineableJSAnyExtension on JSAny?

Helper members to determine if a value is JavaScript undefined or null.

INFO

The members within these extensions may throw depending on the platform. Do not rely on them to be platform-consistent.

JavaScript undefined and JavaScript null are internalized differently based on the backend. When compiling to JavaScript, Dart null can actually be JavaScript undefined or JavaScript null. When compiling to Wasm, that's not the case: there's only one Wasm value null can be. Therefore, when an interop API returns JavaScript null or JavaScript undefined, they are both converted to Dart null when compiling to Wasm, and when you pass a Dart null to an interop API, it is called with JavaScript null. When compiling to JavaScript, Dart null retains its original JavaScript value. Avoid writing code where this distinction between null and undefined matters.

Properties

isDefinedAndNotNull extension no setter

bool get isDefinedAndNotNull

Available on JSAny, provided by the NullableUndefineableJSAnyExtension extension

Implementation

bool get isDefinedAndNotNull => !isUndefinedOrNull;

isNull extension no setter

bool get isNull

Whether this value corresponds to JavaScript null.

INFO

Currently, there is no way to distinguish between JavaScript undefined and JavaScript null when compiling to Wasm. Therefore, this getter should only be used for code that compiles to JavaScript and will throw when compiling to Wasm.

Available on JSAny, provided by the NullableUndefineableJSAnyExtension extension

Implementation

external bool get isNull;

isUndefined extension no setter

bool get isUndefined

Whether this value corresponds to JavaScript undefined.

INFO

Currently, there is no way to distinguish between JavaScript undefined and JavaScript null when compiling to Wasm. Therefore, this getter should only be used for code that compiles to JavaScript and will throw when compiling to Wasm.

Available on JSAny, provided by the NullableUndefineableJSAnyExtension extension

Implementation

external bool get isUndefined;

isUndefinedOrNull extension no setter

bool get isUndefinedOrNull

Available on JSAny, provided by the NullableUndefineableJSAnyExtension extension

Implementation

bool get isUndefinedOrNull => this == null;