Todo List CLI application using Node.js

CLI is a very powerful tool for developers. We will be learning how to create a simple Todo List application for command line. We have seen TodoList as a beginner project in web development and android development but a CLI app is something we don’t often hear about.

Pre-requisites:

• A recent version of Node.js downloaded and installed.
• A text editor, for example, VSCode, atom, etc.
• NPM should be installed.
• Basic understanding of JavaScript, es6 features, etc.

Create a new directory by mkdir <dir-name> and initiate an empty node project by cd into the directory and type the command npm init.

Note: We won’t be using any third-party module in this project.

Project Directory: Now the project directory should consist of two files, package.json, and index.js as shown below:

Some basic functionalities in our Todo List App will be the following:

Implementation: 

Create an index.js file and write down the following code into it

Javascript

// Requiring module
const fs = require('fs');

// Accessing arguments
const args = process.argv;

// The "index.js" is 8 characters long
// so -8 removes last 8 characters
const currentWorkingDirectory = args[1].slice(0, -8);

Explanation: We will be writing todo Tasks in a file called todo.txt and when they will be completed they will be erased from todo.txt and will be written in done.txt. The report will show how many todo has been completed and how many are left. To start with, we will import the fs module which will give us access to the file system.

Then, we will get the arguments passed using process.argv and store them in a variable named args. The process.argv returns an array in which there is the location of node modules, current working directory, and further arguments passed. We will retrieve the cwd by removing the name of the file.

Next, we will check if todo.txt and done.txt already exist in cwd, if not we will create them as shown below:

Javascript

if (fs.existsSync(currentWorkingDirectory + 'todo.txt') === false) {
  let createStream = fs.createWriteStream('todo.txt');
  createStream.end();
}
if (fs.existsSync(currentWorkingDirectory + 'done.txt') === false) {
  let createStream = fs.createWriteStream('done.txt');
  createStream.end();
}

Now we will create different functions for displaying usage, adding todo, deleting todo, etc. They will be called based on the arguments passed.

Info Function: It will display the usage format. It will be called when help is passed as an argument or when no argument is passed.

Javascript

const InfoFunction = () => {
  const UsageText = `
Usage :-
$ node index.js add "todo item"  # Add a new todo
$ node index.js ls               # Show remaining todos
$ node index.js del NUMBER       # Delete a todo
$ node index.js done NUMBER      # Complete a todo
$ node index.js help             # Show usage
$ node index.js report           # Statistics`;

  console.log(UsageText);
};

List Function: It will read the data from todo.txt and display them with a corresponding number. Most Recent is displayed on the top with the largest number.

Javascript

const listFunction = () => {

  // Create a empty array
  let data = [];

  // Read from todo.txt and convert it
  // into a string
  const fileData = fs.readFileSync(
    currentWorkingDirectory + 'todo.txt')
  .toString();

  // Split the string and store into array
  data = fileData.split('\n');

  // Filter the string for any empty lines in the file
  let filterData = data.filter(function (value) {
    return value !== '';
  });

  if (filterData.length === 0) {
    console.log('There are no pending todos!');
  }

  for (let i = 0; i < filterData.length; i++) {
    console.log((filterData.length - i) + '. '
    + filterData[i]);
  }
};

Add Function: It will read the content from todo.txt, add the new todo, and then rewrite it in todo.txt.

Note: Since we don’t have the functionality to set the pointer position in the file while writing and reading files in JavaScript, so every time we add new data we will have to read the data, make the modifications, and then re-write it back.

Javascript

const addFunction = () => {

  // New todo string argument is stored
  const newTask = args[3];

  // If argument is passed
  if (newTask) {

    // Create a empty array
    let data = [];

    // Read the data from file todo.txt and
    // convert it in string
    const fileData = fs
      .readFileSync(currentWorkingDirectory + 'todo.txt')
      .toString();

    // New task is added to previous data
    fs.writeFile(
      currentWorkingDirectory + 'todo.txt',
      newTask + '\n' + fileData,

      function (err) {

        // Handle if there is any error
        if (err) throw err;

        // Logs the new task added
        console.log('Added todo: "' + newTask + '"');
      },
    );
  } else {

    // If argument was no passed
    console.log('Error: Missing todo string. Nothing added!');
  }
};

Delete Function: It will read the data from todo.txt, remove the corresponding task, and re-write the data back in a file.

Javascript

const deleteFunction = () => {

  // Store which index is passed
  const deleteIndex = args[3];

  // If index is passed
  if (deleteIndex) {

    // Create a empty array
    let data = [];

    // Read the data from file and convert
    // it into string
    const fileData = fs
      .readFileSync(currentWorkingDirectory + 'todo.txt')
      .toString();

    data = fileData.split('\n');

    // Filter the data for any empty lines
    let filterData = data.filter(function (value) {
      return value !== '';
    });

    // If delete index is greater than no. of task
    // or less than zero
    if (deleteIndex > filterData.length || deleteIndex <= 0) {
      console.log(
        'Error: todo #' + deleteIndex
            + ' does not exist. Nothing deleted.',
      );
    } else {

      // Remove the task
      filterData.splice(filterData.length - deleteIndex, 1);

      // Join the array to form a string
      const newData = filterData.join('\n');

      // Write the new data back in file
      fs.writeFile(
        currentWorkingDirectory + 'todo.txt',
        newData,
        function (err) {
          if (err) throw err;

          // Logs the deleted index
          console.log('Deleted todo #' + deleteIndex);
        },
      );
    }
  } else {

    // Index argument was no passed
    console.log(
'Error: Missing NUMBER for deleting todo.');
  }
};

Done Function: This function will read data from todo.txt, split it into an array, store the task to be marked as done, delete it from todo.txt, re-write the data back to todo.txt. Now we will write the deleted task we stored along with the current date in done.txt.

Javascript

const doneFunction = () => {

  // Store the index passed as argument
  const doneIndex = args[3];

  // If argument is passed
  if (doneIndex) {

    // Empty array
    let data = [];

    // Create a new date object
    let dateobj = new Date();

    // Convert it to string and slice only the
    // date part, removing the time part
    let dateString = dateobj.toISOString().substring(0, 10);

    // Read the data from todo.txt
    const fileData = fs
      .readFileSync(currentWorkingDirectory + 'todo.txt')
      .toString();

    // Read the data from done.txt
    const doneData = fs
      .readFileSync(currentWorkingDirectory + 'done.txt')
      .toString();

    // Split the todo.txt data
    data = fileData.split('\n');

    // Filter for any empty lines
    let filterData = data.filter(function (value) {
      return value !== '';
    });

    // If done index is greater than no. of task or <=0
    if (doneIndex > filterData.length || doneIndex <= 0) {
      console.log('Error: todo #'
          + doneIndex + ' does not exist.');
    } else {

      // Delete the task from todo.txt
      // data and store it
      const deleted = filterData.splice(
          filterData.length - doneIndex, 1);

      // Join the array to create a string
      const newData = filterData.join('\n');

      // Write back the data in todo.txt
      fs.writeFile(
        currentWorkingDirectory + 'todo.txt',
        newData,
        function (err) {
          if (err) throw err;
        },
      );

      // Write the stored task in done.txt
      // along with date string
      fs.writeFile(
        currentWorkingDirectory + 'done.txt',
        'x ' + dateString + ' ' + deleted
         + '\n' + doneData,
        function (err) {
          if (err) throw err;
          console.log('Marked todo #'
            + doneIndex + ' as done.');
        },
      );
    }
  } else {

    // If argument was not passed
    console.log('Error: Missing NUMBER for'
        + ' marking todo as done.');
  }
};

Report Function: It will read data from todo.txt and done.txt, calculate the number of tasks in each and display how many tasks are completed and how many are pending.

Javascript

const reportFunction = () => {

    // Create empty array for data of todo.txt
    let todoData = [];

    // Create empty array for data of done.txt
    let doneData = [];

    // Create a new date object
    let dateobj = new Date();

    // Slice the date part
    let dateString = dateobj.toISOString().substring(0, 10);

    // Read data from both the files
    const todo = fs.readFileSync(currentWorkingDirectory
                + 'todo.txt').toString();
    const done = fs.readFileSync(currentWorkingDirectory
                + 'done.txt').toString();

    // Split the data from both files
    todoData = todo.split('\n');

    doneData = done.split('\n');
    let filterTodoData = todoData.filter(function(value) {
        return value !== '';
    });

    let filterDoneData = doneData.filter(function(value) {

        // Filter both the data for empty lines
        return value !== '';
    });

    console.log(
        dateString +
        ' ' +
        'Pending : ' +
        filterTodoData.length +
        ' Completed : ' +
        filterDoneData.length,
        // Log the stats calculated
    );
};

Now Since we have created all the functions, Now we will just put a switch statement and call functions based on arguments passed.

Javascript

switch (args[2]) {
  case 'add': {
    addFunction();
    break;
  }

  case 'ls': {
    listFunction();
    break;
  }

  case 'del': {
    deleteFunction();
    break;
  }

  case 'done': {
    doneFunction();
    break;
  }

  case 'help': {
    InfoFunction();
    break;
  }

  case 'report': {
    reportFunction();
    break;
  }

  default: {
    InfoFunction();
    // We will display help when no
    // argument is passed or invalid
    // argument  is passed
  }
}

Filename: index.js Our final index.js file will look like the following:

Javascript

const fs = require('fs');

const args = process.argv;

// The "index.js" is 8 characters long so -8
// removes last 8 characters
const currentWorkingDirectory = args[1].slice(0, -8);


if (fs.existsSync(currentWorkingDirectory +
        'todo.txt') === false) {
    let createStream = fs.createWriteStream('todo.txt');
    createStream.end();
}
if (fs.existsSync(currentWorkingDirectory +
        'done.txt') === false) {
    let createStream = fs.createWriteStream('done.txt');
    createStream.end();
}

const InfoFunction = () => {
    const UsageText = `
Usage :-
$ node index.js add "todo item"  # Add a new todo
$ node index.js ls               # Show remaining todos
$ node index.js del NUMBER       # Delete a todo
$ node index.js done NUMBER      # Complete a todo
$ node index.js help             # Show usage
$ node index.js report           # Statistics`;

    console.log(UsageText);
};

const listFunction = () => {

    // Create a empty array
    let data = [];

    // Read from todo.txt and convert it into a string
    const fileData = fs
        .readFileSync(currentWorkingDirectory +
            'todo.txt').toString();

    // Split the string and store into array
    data = fileData.split('\n');

    // Filter the string for any empty lines in the file
    let filterData = data.filter(function(value) {
        return value !== '';
    });

    if (filterData.length === 0) {
        console.log('There are no pending todos!');
    }
    for (let i = 0; i < filterData.length; i++) {
        console.log((filterData.length - i) + '. ' +
            filterData[i]);
    }
};

const addFunction = () => {

    // New todo string argument is stored
    const newTask = args[3];

    // If argument is passed
    if (newTask) {

        // create a empty array
        let data = [];

        // Read the data from file todo.txt and
        // convert it in string
        const fileData = fs
            .readFileSync(currentWorkingDirectory +
                'todo.txt').toString();

        // New task is added to previous data
        fs.writeFile(
            currentWorkingDirectory + 'todo.txt',
            newTask + '\n' + fileData,

            function(err) {

                // Handle if there is any error
                if (err) throw err;

                // Logs the new task added
                console.log('Added todo: "' + newTask + '"');
            },
        );
    } else {

        // If argument was no passed
        console.log('Error: Missing todo string.' +
            ' Nothing added!');
    }
};

const deleteFunction = () => {

    // Store which index is passed
    const deleteIndex = args[3];

    // If index is passed
    if (deleteIndex) {

        // Create a empty array
        let data = [];

        // Read the data from file and convert
        // it into string
        const fileData = fs
            .readFileSync(currentWorkingDirectory +
                'todo.txt').toString();

        data = fileData.split('\n');
        let filterData = data.filter(function(value) {

            // Filter the data for any empty lines
            return value !== '';
        });

        // If delete index is greater than no. of task
        // or less than zero
        if (deleteIndex > filterData.length || deleteIndex <= 0) {
            console.log(
                'Error: todo #' + deleteIndex +
                ' does not exist. Nothing deleted.',
            );

        } else {

            // Remove the task
            filterData.splice(filterData.length - deleteIndex, 1);

            // Join the array to form a string
            const newData = filterData.join('\n');

            // Write the new data back in file
            fs.writeFile(
                currentWorkingDirectory + 'todo.txt',
                newData,
                function(err) {
                    if (err) throw err;

                    // Logs the deleted index
                    console.log('Deleted todo #' + deleteIndex);
                },
            );
        }
    } else {

        // Index argument was no passed
        console.log('Error: Missing NUMBER for deleting todo.');
    }
};

const doneFunction = () => {

    // Store the index passed as argument
    const doneIndex = args[3];

    // If argument is passed
    if (doneIndex) {

        // Empty array
        let data = [];

        // Create a new date object
        let dateobj = new Date();

        // Convert it to string and slice only the
        //  date part, removing the time part
        let dateString = dateobj.toISOString()
                    .substring(0, 10);

        // Read the data from todo.txt
        const fileData = fs
            .readFileSync(currentWorkingDirectory
                + 'todo.txt').toString();

        // Read the data from done.txt
        const doneData = fs
            .readFileSync(currentWorkingDirectory
                + 'done.txt').toString();

        // Split the todo.txt data
        data = fileData.split('\n');

        // Filter for any empty lines
        let filterData = data.filter(function(value) {
            return value !== '';
        });

        // If done index is greater than
        // no. of task or <=0
        if (doneIndex > filterData.length || doneIndex <= 0) {
            console.log('Error: todo #' + doneIndex
                    + ' does not exist.');

        } else {

            // Delete the task from todo.txt data
            // and store it
            const deleted = filterData.splice(
                filterData.length - doneIndex, 1);

            // Join the array to create a string
            const newData = filterData.join('\n');

            // Write back the data in todo.txt
            fs.writeFile(
                currentWorkingDirectory + 'todo.txt',
                newData,

                function(err) {
                    if (err) throw err;
                },
            );
            fs.writeFile(

                // Write the stored task in done.txt
                // along with date string
                currentWorkingDirectory + 'done.txt',
                'x ' + dateString + ' ' + deleted
                                + '\n' + doneData,
                function(err) {
                    if (err) throw err;
                    console.log('Marked todo #'
                        + doneIndex + ' as done.');
                },
            );
        }
    } else {
        // If argument was not passed
        console.log('Error: Missing NUMBER for '
                +  'marking todo as done.');
    }
};

const reportFunction = () => {

    // Create empty array for data of todo.txt
    let todoData = [];

    // Create empty array for data of done.txt
    let doneData = [];

    // Create a new date object
    let dateobj = new Date();

    // Slice the date part
    let dateString = dateobj.toISOString()
                    .substring(0, 10);

    // Read data from both the files
    const todo = fs.readFileSync(
            currentWorkingDirectory
            + 'todo.txt').toString();

    const done = fs.readFileSync(
        currentWorkingDirectory
        + 'done.txt').toString();

    // Split the data from both files
    todoData = todo.split('\n');

    doneData = done.split('\n');
    let filterTodoData = todoData.filter(function(value) {
        return value !== '';
    });
    let filterDoneData = doneData.filter(function(value) {
        return value !== '';
        // Filter both the data for empty lines
    });
    console.log(
        dateString +
        ' ' +
        'Pending : ' +
        filterTodoData.length +
        ' Completed : ' +
        filterDoneData.length,
        // Log the stats calculated
    );
};

switch (args[2]) {
    case 'add':
        {
            addFunction();
            break;
        }

    case 'ls':
        {
            listFunction();
            break;
        }

    case 'del':
        {
            deleteFunction();
            break;
        }

    case 'done':
        {
            doneFunction();
            break;
        }

    case 'help':
        {
            InfoFunction();
            break;
        }

    case 'report':
        {
            reportFunction();
            break;
        }

    default:
        {
            InfoFunction();
            // We will display help when no
            // argument is passed or invalid
            // argument  is passed
        }
}

Step to run the application:

Run the index.js file using the following command:

node index.js

Output: