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wasmer/lib/js-api/README.md
2021-06-21 21:42:09 -07:00

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# `wasmer-js` [![Build Status](https://github.com/wasmerio/wasmer/workflows/build/badge.svg?style=flat-square)](https://github.com/wasmerio/wasmer/actions?query=workflow%3Abuild) [![Join Wasmer Slack](https://img.shields.io/static/v1?label=Slack&message=join%20chat&color=brighgreen&style=flat-square)](https://slack.wasmer.io) [![MIT License](https://img.shields.io/github/license/wasmerio/wasmer.svg?style=flat-square)](https://github.com/wasmerio/wasmer/blob/master/LICENSE) [![crates.io](https://img.shields.io/crates/v/wasmer-js.svg)](https://crates.io/crates/wasmer-js)
[`Wasmer`](https://wasmer.io/) is the most popular
[WebAssembly](https://webassembly.org/) runtime for Rust (...and also
the fastest). This runtime is an adapted version of the Wasmer API that compiles to
WebAssembly via `wasm-bindgen`.
`wasmer-js` uses the same WebAssembly runtime of your environment (browser or Node.js).
## Usage
```rust
use wasmer_js::{Store, Module, Instance, Value, imports};
fn main() -> anyhow::Result<()> {
let module_wat = r#"
(module
(type $t0 (func (param i32) (result i32)))
(func $add_one (export "add_one") (type $t0) (param $p0 i32) (result i32)
get_local $p0
i32.const 1
i32.add))
"#;
let store = Store::default();
let module = Module::new(&store, &module_wat)?;
// The module doesn't import anything, so we create an empty import object.
let import_object = imports! {};
let instance = Instance::new(&module, &import_object)?;
let add_one = instance.exports.get_function("add_one")?;
let result = add_one.call(&[Value::I32(42)])?;
assert_eq!(result[0], Value::I32(43));
Ok(())
}
```
## Config flags
Wasmer has the following configuration flags:
* `wat` (enabled by default): It allows to read WebAssembly files in their text format.
*This feature is normally used only in development environments*
# Build
You can use `wasm-pack` to build wasmer-js:
```
wasm-pack build --release
```
> The provided `wasmer_js.wasm` file should weight around 75kB when optmized via `wasm-opt` and stripped via `wasm-strip`, so it's relatively slim.
# Test
```
wasm-pack test --node
```
---
Made with ❤️ by the Wasmer team, for the community