WebAssembly (WASM) Runner

Write a Rust program, compile it with cargo build --release --target wasm32-unknown-unknown and upload the resulting *.wasm file here to call its functions with JavaScript.

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Create a new cargo crate with cargo init --lib folder-name.
cd into the folder-name folder.
Replace Cargo.toml with the below code.

[package]
name = "folder-name"
version = "1.0.0"
edition = "2024"

[lib]
crate-type = ["cdylib", "rlib"]

[dependencies]
wasm-bindgen = "0.2"

Put your Rust code in src/lib.rs.
Below is the example Rust program used as the default .wasm file below.

unsafe extern "C" {
    fn alert(s: i32) -> ();
    fn _print(ptr: *const u8, len: i32) -> ();
    fn _println(ptr: *const u8, len: i32) -> ();
}

// Use imported helper functions to make simple print(str) function
unsafe fn println(str: &str) {
    _println(str.as_ptr(), str.len() as i32);
}
unsafe fn print(str: &str) {
    _print(str.as_ptr(), str.len() as i32);
}

#[unsafe(no_mangle)]
pub unsafe fn greet() {
    alert(1);
    println("Hello from Rust!");
}

#[unsafe(no_mangle)]
pub fn first_sq_over(x: u32) -> u32 {
    let mut n: u32 = 0;
    loop {
        let sq = n * n;
        if sq > x {
            return sq;
        }
        n += 1;
    }
}

#[unsafe(no_mangle)]
pub unsafe fn main() {
    println("main() called");
}

Your code can use the methods imported at the top of the above example.
Note: To use the print functions, refer to the above example.
Compile it using the command: cargo build --release --target wasm32-unknown-unknown
Grab the file target/wasm32-unknown-unknown/release/folder-name.wasm and upload it here.
If your file has a main method, it will be called automatically.
Use the JavaScript editor below to run JS and call your WASM functions.

Loading wasm-test.wasm…