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Using the Node Host SDK

Check your installation

Please be sure you've installed Extism before continuing with this guide.

1. Install the Node module​

Install via npm:

npm install @extism/extism --save

2. Import the module and use the APIs​

Count Vowels Plugin

code.wasm in this example is our example plugin that counts vowels. If you want to run this, download it first and set the path:

curl https://raw.githubusercontent.com/extism/extism/main/wasm/code.wasm > code.wasm
index.js
const { withContext, Context } = require('@extism/extism');
const { readFileSync } = require('fs');

withContext(async function (context) {
  let wasm = readFileSync('../wasm/code.wasm');
  let p = context.plugin(wasm);

  if (!p.functionExists('count_vowels')) {
    console.log("no function 'count_vowels' in wasm");
    process.exit(1);
  }

  let buf = await p.call('count_vowels', process.argv[2] || 'this is a test');
  console.log(JSON.parse(buf.toString())['count']);
  p.free();
});

// or, use a context like this:
let ctx = new Context();
let wasm = readFileSync('../wasm/code.wasm');
let p = ctx.plugin(wasm);
// ... where the context can be passed around to various functions etc.

Need help?​

If you've encountered a bug or think something is missing, please open an issue on the Extism GitHub repository.

There is an active community on Discord where the project maintainers and users can help you. Come hang out!