WebAssembly.Exception.prototype.is()

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨May 2022⁩.

Theis() prototype method of theException object can be used to test if theException matches a given tag.

The method might be used to test that a tag is correct before passing it toException.prototype.getArg() to get the passed values.It can be used on tags created in JavaScript or created in WebAssembly code and exported to JavaScript.

Note:It is not enough that the tag has an identical sequence of data types — it must have the sameidentity (be the same tag) as was used to create the exception.

Syntax

is(tag)

Parameters

tag: AWebAssembly.Tag that can be checked to verify the type of the exception.

Return value

A booleantrue if the specified tag matches the exception, andfalse otherwise.

Examples

The code below shows how to useis() to verify that a tag matches anException.

// Create tag and use it to create an exceptionconst tag1 = new WebAssembly.Tag({ parameters: ["i32", "f64"] });const exception1 = new WebAssembly.Exception(tag1, [42, 42.3]);// Verify that "tag1" matches this exceptionconsole.log(`Tag1: ${exception1.is(tag1)}`);// Log output:// Tag1: true

We can also demonstrate that this exception will not match another tag even if the tag is created with the same parameters.

// Create a new tag (with same parameters) and verify it does not match the exceptionconst tag2 = new WebAssembly.Tag({ parameters: ["i32", "f64"] });console.log(`Tag2: ${exception1.is(tag2)}`);// Log output:// Tag2: false