Node scripting challenge

Write custom Node scripts to automate tasks in your terminal

  • node
  • shell
  • scripting
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Node isn’t just used for HTTP servers—it’s a fully-fledged programming language that can do almost anything. Let’s see how we can use it to create useful scripts we can run in our terminal.

We could recreate the built-in ls program using Node’s filesystem module:

// ls.js
const fs = require("fs/promises");

const currentDir = process.cwd();

fs.readdir(currentDir).then((files) => {
  files.forEach((file) => console.log(file));
});

We’re importing "fs/promises" because Node’s standard "fs" module uses callbacks. We get the directory the script was run from using process.cwd() (“current working directory”). Finally we use fs.readdir to get the names of every file in the directory and log them.

You can run this script using node ./path/to/ls.js. It should list the contents of whatever directory you’re currently inside in your terminal.

We’re currently running it by passing the file to our node program. However we can make the script directly executable by doing two things:

First we must add a “shebang” to the top of the file. This is a special comment that tells the terminal which program it should use to run a script.

#! /usr/bin/env node

// ...

Second you need to change the file’s permissions to make it “executable”. You can do so with:

chmod +x ls.js

You can now run this script with ./path/to/ls.js. You actually don’t even need the .js extension anymore, since the shebang tells your terminal that it’s a Node file. So you could rename it to just ls and run it with ./path/to/ls.

Challenge

Write a Node script that creates a new HTML file containing all the boilerplate code you normally need. The filename should be passed in as an argument. E.g. running this command:

./create-html hello-world

should create a new file named hello-world.html containing:

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <title>hello world</title>
  </head>
  <body>
    <h1>hello world</h1>
  </body>
</html>

You can access the arguments passed to a script using process.argv.

You can create new files using fs.writeFile:

fs.writeFile("my-file-name.txt", "hello world").then(() => {
  console.log("finished");
});
Toggle answer 
#! /usr/bin/env node

const fs = require("fs/promises");

const filename = process.argv[2];
const title = filename.replace(/-/g, " ");

const contents = `<!doctype html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <title>${title}</title>
  </head>
  <body>
    <h1>${title}</h1>
  </body>
</html>`;

fs.writeFile(filename + ".html", contents).then(() => {
  console.log(`Created ${filename}.html successfully!`);
});