webassembly-types

Better types for interacting with WebAssembly

Install

Using npm:

npm install --save webassembly-types

or using yarn:

yarn add webassembly-types

Usage

API:

const types = require("webassembly-types");

types.i32(12);
types.i64(12);
const a = types.i64(12n);

// call an export
instance.exports.fn(a);

Why

stricter range checks

To be consistent with JavaScript, out-of-range numbers passed in WebAssembly do silently overflow. This can be pretty error-prone, as shown by the following example:

(module
  (memory 1)
  (func (export "load") (param i32) (result i32)
    (get_local 0)
    (i32.load)
  )
)

instance.exports.load(4294967296);

Will load at offset 0 because it overflowed at the Wasm boundary.

Using the i32 from this lib will make it throw instead.

simpler i64

In JavaScript BigInt are not convertible to Number, this can be annoying when trying to keep your JavaScript<>Wasm code generic.

For instance, the previous example could be compiled for both 32-bit and 64-bit address space. In 64-bit mode is would look like the following:

(module
  (memory 1)
  (func (export "load") (param i64) (result i64)
    (get_local 0)
    (i64.load)
  )
)

The call here, wouldn't work anymore (it will throw instead):

instance.exports.load(4294967296);

Using the lib:

instance.exports.load(i64(4294967296));