Install a javascript function as an executable

installFn.ts

import cache_dir from "https://deno.land/x/dir@1.5.1/cache_dir/mod.ts";
import { ensureDirSync } from "https://deno.land/std@0.152.0/fs/ensure_dir.ts";

export interface Options {
  prelude?: string;
  permissions?: string[];
}

// deno-lint-ignore no-explicit-any
export default function installFn(fn: any, options?: Options) {
  const name = fn.name;
  if (!name) {
    throw "fn name is required";
  }
  const body: string = fn.toString();

  let content;
  if (body.includes("=>")) {
    content = `
        const ${name} = ${body}
        const output = ${name}(...Deno.args)
        console.log(output)
        `;
  } else {
    // TODO
    throw "unrecognized function type";
  }

  if (options?.prelude) {
    content = options.prelude + "\n" + content;
  }

  const installDir = `${cache_dir()}/deno-install-fn/`;
  ensureDirSync(installDir);
  const fnPath = `${installDir}/${name}.ts`;
  Deno.writeTextFileSync(fnPath, content);
  Deno.spawnSync("deno", {
    args: ["fmt", fnPath],
  });
  Deno.spawnSync("deno", {
    args: options?.permissions
      ? ["install", "-f", ...options.permissions, fnPath]
      : ["install", "-f", fnPath],
    stdout: "inherit",
    stderr: "inherit",
  });

  console.log(`%c${name}%c was succefully installed!`, "color:blue", "");
}

How it works

1- create a script with the name of the function
2- Write the script content (to $cache/deno-install-fn/script): Evaluate Deno.args as input to the function body and write it to stdout
3- deno install scriptPath i you have ~/.deno/bin in your path , this make it very convenient as the function will become immediately available