docs.sheetjs.com/docz/docs/03-demos/42-engines/21-boa.md

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---
title: Rust + Boa
pagination_prev: demos/bigdata/index
pagination_next: solutions/input
---
import current from '/version.js';
import CodeBlock from '@theme/CodeBlock';
:::danger pass
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In a production application, it is strongly recommended to use a binding for a
more performant engine like [`v8`](/docs/demos/engines/v8#rust)
:::
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[Boa](https://boajs.dev/) is a JavaScript engine written in Rust.
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[SheetJS](https://sheetjs.com) is a JavaScript library for reading and writing
data from spreadsheets.
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The ["Complete Example"](#complete-example) section creates a command-line tool
for reading data from spreadsheets and generating CSV rows.
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## Integration Details
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### Initialize Boa
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A JS context can be constructed in one line:
```rust
use boa_engine::Context;
/* initialize */
let context = &mut Context::default();
```
The following helper function evaluates strings as JS code:
```rust
use std::string::String;
use boa_engine::{Context, Source, JsError};
/* simple wrapper to evaluate code snippets */
fn eval_code(c: &mut Context, code: &str) -> Result<String, JsError> {
let src = Source::from_bytes(code);
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match c.eval(src) {
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Ok(res) => { return Ok(res.to_string(c).unwrap().to_std_string_escaped()); }
Err(e) => { return Err(e); }
};
}
```
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### Load SheetJS Scripts
The [SheetJS Standalone scripts](/docs/getting-started/installation/standalone)
can be parsed and evaluated in a Boa context.
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Boa provides a special helper to read source code from a path:
```rust
use std::path::Path;
use std::string::String;
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use boa_engine::{js_string, Context, Source, JsError};
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/* simple wrapper to evaluate an entire script file */
fn eval_file(c: &mut Context, path: &str) -> Result<String, JsError> {
let src = Source::from_filepath(Path::new(path)).unwrap();
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match c.eval(src) {
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Ok(res) => { return Ok(res.to_string(c).unwrap().to_std_string_escaped()); }
Err(e) => { return Err(e); }
};
}
// ...
/* load library */
match eval_file(context, "./xlsx.full.min.js") {
Ok(_res) => {}
Err(e) => { return eprintln!("Uncaught {e}"); }
}
```
To confirm the library is loaded, `XLSX.version` can be inspected:
```rust
/* get version string */
match eval_code(context, "XLSX.version") {
Ok(res) => { println!( "SheetJS library version {}", res); }
Err(e) => { return eprintln!("Uncaught {e}"); }
}
```
### Reading Files
Boa supports `ArrayBuffer` natively. This snippet reads data from a file into
`Vec<u8>` and stores the data as an `ArrayBuffer` in global scope:
```rust
/* read file */
let data: Vec<u8> = fs::read("pres.xlsx").unwrap();
let array: JsArrayBuffer = JsArrayBuffer::from_byte_block(data, context).unwrap();
let attrs = Attribute::WRITABLE | Attribute::ENUMERABLE | Attribute::CONFIGURABLE;
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context.register_global_property(js_string!("buf"), array, attrs);
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/* parse with SheetJS */
match eval_code(context, "void (globalThis.wb = XLSX.read(buf))") {
Ok(_res) => { }
Err(e) => { return eprintln!("Uncaught {e}"); }
}
```
`wb` will be a variable in the JS environment that can be inspected using the
various SheetJS API functions.
## Complete Example
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:::note Tested Deployments
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This demo was tested in the following deployments:
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| Architecture | Boa | Date |
|:-------------|:---------|:-----------|
| `darwin-x64` | `0.18.0` | 2024-03-15 |
| `darwin-arm` | `0.17.3` | 2023-10-20 |
| `win10-x64` | `0.17.3` | 2024-03-04 |
| `win11-arm` | `0.17.3` | 2023-12-01 |
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| `linux-x64` | `0.18.0` | 2024-03-21 |
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| `linux-arm` | `0.17.3` | 2023-12-01 |
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:::
1) Create a new project:
```bash
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cargo new sheetjs-boa
cd sheetjs-boa
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cargo run
```
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2) Add the `boa_engine` crate:
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```bash
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cargo add boa_engine
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```
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3) Download the SheetJS Standalone script and move to the project directory:
<ul>
<li><a href={`https://cdn.sheetjs.com/xlsx-${current}/package/dist/xlsx.full.min.js`}>xlsx.full.min.js</a></li>
</ul>
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<CodeBlock language="bash">{`\
curl -LO https://cdn.sheetjs.com/xlsx-${current}/package/dist/xlsx.full.min.js`}
</CodeBlock>
4) Download [`main.rs`](pathname:///boa/main.rs) and replace `src/main.rs`:
```bash
curl -L -o src/main.rs https://docs.sheetjs.com/boa/main.rs
```
5) Download [the test file](https://sheetjs.com/pres.xlsx) and run:
```bash
curl -LO https://sheetjs.com/pres.xlsx
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cargo run --release
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```
After a short wait, the contents will be displayed in CSV form.
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:::caution pass
The default debug build is not optimized and can elicit stack overflow errors.
It is strongly encouraged to use `--release` when possible.
:::