minimal module

.gitignore

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+node_modules

__tests__/emitter.ts

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+import { emitter } from "../src/emitter";
+
+describe("emitter", () => {
+  test("doesn't barf when loading the module", async () => {
+    const wasm = emitter();
+    await WebAssembly.instantiate(wasm);
+  });
+});

jest.config.js

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+module.exports = {
+  preset: "ts-jest",
+  testEnvironment: "node"
+};

package.json

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+{
+  "name": "chasm",
+  "version": "1.0.0",
+  "main": "index.js",
+  "author": "Colin Eberhardt <colin.eberhardt@gmail.com>",
+  "license": "MIT",
+  "devDependencies": {
+    "@types/jest": "^24.0.11",
+    "@types/node": "^11.13.4",
+    "@types/webassembly-js-api": "^0.0.3",
+    "jest": "^24.7.1",
+    "ts-jest": "^24.0.2",
+    "typescript": "^3.4.3"
+  },
+  "scripts": {
+    "test": "jest"
+  }
+}

src/emitter.ts

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+
+// https://webassembly.github.io/spec/core/binary/modules.html#binary-module
+const magicModuleHeader = [0x00, 0x61, 0x73, 0x6d];
+const moduleVersion = [0x01, 0x00, 0x00, 0x00];
+
+export const emitter: Emitter = () => {
+  const buffer = [
+    ...magicModuleHeader,
+    ...moduleVersion,
+  ];
+  return Uint8Array.from(buffer);
+};

src/types/emitter.ts

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+interface Emitter {
+  (): Uint8Array;
+}

tsconfig.json

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+{
+  "compilerOptions": {
+    "outDir": "./built",
+    "allowJs": true,
+    "lib": ["es2017", "dom"],
+    "module": "commonjs",
+    "target": "es2017",
+    "noImplicitAny": true
+  },
+  "include": ["./src/**/*", "./__tests__/**/*"]
+}