NullableUndefineableJSAnyExtension extension - dart:js_interop library (original) (raw)

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

Note

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 andundefined matters.

on

• JSAny?

Properties

isDefinedAndNotNull → bool

Available on JSAny?, provided by the NullableUndefineableJSAnyExtension extension

no setter

isNull → bool

Available on JSAny?, provided by the NullableUndefineableJSAnyExtension extension

Whether this value corresponds to JavaScript null.

no setter

isUndefined → bool

Available on JSAny?, provided by the NullableUndefineableJSAnyExtension extension

Whether this value corresponds to JavaScript undefined.

no setter

isUndefinedOrNull → bool

Available on JSAny?, provided by the NullableUndefineableJSAnyExtension extension

no setter