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In this tutorial, you’ll learn how to compile a simple C program into WebAssembly (WASM) using Emscripten and then execute it in a Node.js environment. The workflow mirrors browser-based builds, but outputs a JavaScript “glue” file suitable for server-side execution.

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Prerequisites

  • Node.js (tested with v14.18.2)
  • Emscripten SDK with emcc available in your PATH
Before you begin, make sure you’ve installed Node.js and set up the Emscripten SDK.
Run emcc --version to verify your installation.
Check your Node.js version: 
node -v
# Expected output:
# v14.18.2

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1. Write the C Source

Create a file named helloworld.c with the following contents: 
#include <stdio.h>

int main() {
    printf("Hello World\n");
    return 0;
}

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2. Compile to WASM for Node.js

Use Emscripten’s emcc compiler to generate both the WebAssembly binary and the JavaScript loader: 
emcc /path/to/helloworld.c -o /path/to/helloworld.js
This command produces:
FileDescription
helloworld.jsJavaScript “glue” code that locates, loads, and runs the WASM asset
helloworld.wasmCompiled WebAssembly module
The top of helloworld.js looks like this: 
var Module = typeof Module != 'undefined' ? Module : {};
// …glue code to locate and instantiate helloworld.wasm…

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3. Execute the WASM Module in Node.js

Run your generated loader script with Node: 
node /path/to/helloworld.js
# Output:
# Hello World
That’s all! You’ve successfully compiled a C program into WASM and executed it on the server with Node.js.

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