Remove Specific Line in Vim

• Notes
• Vim

A Brief Intro

In this post, we will talk about how to remove specific line in vim. We will be using this javascript snippet code as an example:

const app = require('./jest-example');
const math = require('./math');

describe('app operation', () => {
  const multiplyMock = jest.spyOn(math, 'multiply');
  multiplyMock.mockReturnValue('itu');

  test('call math.add()', () => {
    const add = jest.spyOn(math, 'add');

    add.mockImplementation(() => 'anu');
    console.log(app.doAdd(1, 2));
    expect(app.doAdd(1, 2)).toBe('anu');

    add.mockRestore();
    console.log(app.doAdd(1, 2));
    expect(app.doAdd(1, 2)).toBe(3);
  });

  test('call math.subtract()', () => {
    const subtract = jest.spyOn(math, 'subtract');

    subtract.mockImplementation(() => 'nganu');
    console.log(app.doSubtract(1, 2));
    expect(app.doSubtract(1, 2)).toBe('nganu');
  });

  test('call math.subtract() again', () => {
    console.log(app.doSubtract(1, 2));
  });

  test('call math.multiply()', () => {
    console.log(app.doMultiply(1, 2));
  });
});

And the goal is to remove line that has console.log() in it. Let’s get started!

Global Command

The first solution is that, we can use global command to delete the line that has console.log() like this:

:g/console.log/d

Please keep in mind that the term delete in vim, means cut. So, rather than deleting the content, vim will put that into the unnamed register. For more info about unnamed register, we can check on :help registers.

So, if we didn’t want to clutter our unnamed register, we can use black hole register (yup, that’s a thing) which actually delete rather than cut like this:

:g/console.log/d_

On a side note, we don’t need to use / as the separator between command and pattern, we can use most characters except \, ", or |. If we use vim9 script, we can use # as a separator either, so please keep that in mind. For more info, we can check on :help pattern-delimiter.

In other words, we can write the previous global command, like this:

:g;console.log;d_

The global command that we just gone through will delete all the console.log in current file. If we want to specify the area of console.log we want to delete, we can add range to global command.

Let’s take a look at the snippet we are using:

const app = require('./jest-example');
const math = require('./math');

describe('app operation', () => {
  const multiplyMock = jest.spyOn(math, 'multiply');
  multiplyMock.mockReturnValue('itu');

  test('call math.add()', () => {
    const add = jest.spyOn(math, 'add');

    add.mockImplementation(() => 'anu');
    console.log(app.doAdd(1, 2));
    expect(app.doAdd(1, 2)).toBe('anu');

    add.mockRestore();
    console.log(app.doAdd(1, 2));
    expect(app.doAdd(1, 2)).toBe(3);
  });

  test('call math.subtract()', () => {
    const subtract = jest.spyOn(math, 'subtract');

    subtract.mockImplementation(() => 'nganu');
    console.log(app.doSubtract(1, 2));
    expect(app.doSubtract(1, 2)).toBe('nganu');
  });

  test('call math.subtract() again', () => {
    console.log(app.doSubtract(1, 2));
  });

  test('call math.multiply()', () => {
    console.log(app.doMultiply(1, 2));
  });
});

And let’s say that our cursor in the line test('call math.subtract()', () => { and we want to delete the console.log in test('call math.add()', () => { which is before the line we’re currently in.

With that in mind, we can do something like this:

:?test?;/});/g;console.log;d_

Here’s the breakdown of those command:

• ?test? will search word test on previous line.
• ; after ?test? is a special offset which tell vim that we will use another search command. For more info, we can check :help //;.
• /});/ will search after the result of previous search.
• g;console.log;d_ is a global command to delete console.log in the scope of previous search.

Substitute Command

The downside of global command is that there’s no confirm option, so we might delete something we don’t want to. If we want a confirm option, we can use substitute command.

If we want to delete all the console.log in current file, we can do it like this:

:%s;.*console.log.*\n;;c

Here’s the breakdown of those command:

• % symbol to tell vim that the range is the current file or all the line in the file.
• s is the abbreviation of substitute command.
• .*console.log.*\n is the pattern that select the line that has console.log in it, which include the newline character at the end.
• ;; is basically telling vim to replace it with nothing.
• c is a confirm option.

We can also combine substitute command with global command, like this:

:g;console.log;s;.*\n;;c

Conclusion

There’s a lot of possibility with global and substitute command and we won’t be able to cover all of those in one blog post. So, i will leave it to you to explore those possibility.

You might want to learn regular expression to enhance the global and substitute command experience.

Alright, that’s it for this post. Thank you for reading!