06 — Wire the CLI

Goal

Replace the beginner cli.js with a full command switch that wires every function from todo.js to a named command. The file path can be overridden with the TODO_FILE environment variable for easy testing.

The full cli.js

// cli.js
const {
  readTodos, writeTodos, addTodo, completeTodo, removeTodo, pendingTodos,
  seedTodos, formatList,
} = require("./todo");

const FILE = process.env.TODO_FILE || "todos.json";
const [cmd, ...rest] = process.argv.slice(2);

if (cmd === "add") {
  const text = rest.join(" ");
  if (!text) {
    console.error('usage: node cli.js add "text"');
    process.exit(1);
  }
  writeTodos(FILE, addTodo(readTodos(FILE), text));
  console.log(`Added: ${text}`);
} else if (cmd === "done") {
  const n = Number(rest[0]) - 1;
  writeTodos(FILE, completeTodo(readTodos(FILE), n));
  console.log(`Done: ${n + 1}`);
} else if (cmd === "remove") {
  const n = Number(rest[0]) - 1;
  writeTodos(FILE, removeTodo(readTodos(FILE), n));
  console.log(`Removed: ${n + 1}`);
} else if (cmd === "list") {
  const todos = readTodos(FILE);
  console.log(
    formatList(rest[0] === "--pending" ? pendingTodos(todos) : todos),
  );
} else if (cmd === "seed") {
  seedTodos().then((seeded) => {
    writeTodos(FILE, seeded);
    console.log(`Seeded ${seeded.length} todos`);
  });
} else {
  console.error("commands: add, done, remove, list [--pending], seed");
  process.exit(1);
}

Key patterns

process.argv.slice(2) — argv[0] is node, argv[1] is the script path, so arguments start at index 2. Destructuring [cmd, ...rest] gives the command name and any trailing words.

1-based → 0-based index — users type node cli.js done 1 (human-friendly 1-based), so Number(rest[0]) - 1 converts to the 0-based array index.

TODO_FILE env var — lets you point to a different file without touching the code:

TODO_FILE=test.json node cli.js add "isolated test item"

Checkpoint walkthrough

node cli.js seed
# Seeded 3 todos

node cli.js list
# 1. [ ] delectus aut autem
# 2. [ ] quis ut nam facilis et possimus et asperiores
# 3. [ ] fugiat veniam minus

node cli.js done 1
# Done: 1

node cli.js list --pending
# 1. [ ] quis ut nam facilis et possimus et asperiores
# 2. [ ] fugiat veniam minus

node cli.js remove 2
# Removed: 2

node cli.js list
# 1. [x] delectus aut autem
# 2. [ ] fugiat veniam minus

TIP

list --pending re-numbers from 1 in the display but the underlying array indices stay fixed — remove 2 after filtering may target a different item than you expect. A future improvement would be to filter then persist the filtered array before renumbering.