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    Configure Prettier to Automatically Format Code

    Andy Van SlaarsAndy Van Slaars

    Consistent code format can make a project easier to maintain. What that format is can be largely subjective, but rather than spend a bunch of valuable time "bike shedding" over semi-colons or no semis and spaces vs tab, we should just let the tools handle this. In this lesson we'll configure Prettier to format our code for us.



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    Instructor: 00:00 This index.js file works, but the formatting is a disaster. I have extra indentation all over the place, extra lines where I don't need them. Some of lines are ending with semicolons some are not. This parenthesis is hanging out all the way down here.

    00:14 I could manually fix all these problems, but I'd like to introduce an automated solution so that I don't have to worry about this, and I can let the editor and my build tools fix the formatting for me. To do that, we're going to install Prettier. We'll do npm i-key prettier. We're also going to install pretty-quick.

    00:39 With those installed, let's go into our package.json. In my scripts, I'm going to create a script I'm going to call format. Format is going to use pretty-quick to run Prettier against my code. I'm going to make this command pretty-quick. I'll save that file.

    00:59 Back in my terminal, I'm going to do an npm run format. We'll see that it's finding changed files since git revision, which is my last git commit. It'll let me know that it found three changed files, and that it's fixing source index.js.

    01:18 If I look at that index.js file, now that formatting has mostly been cleaned up. I have consistent semicolons at the end of each line. It's gotten rid of all the extra spaces that I had before this parenthesis. It's left this space, and that's OK. We can take that out manually if we don't want it there, but if we wanted it, Prettier won't touch it.

    01:40 We have this automatic formatting, and that's great. That means we don't have to worry about it. Let's say I prefer to not have semicolons, and I like using single quotes instead of double quotes in my JavaScript. We can fix that with a Prettier config file.

    01:53 In the root of my project, I'm going to add a new file, and I'm going to call this one .prettierrc. In this file, I'm going to give it a JSON object, and I'm going to define a couple of settings here.

    02:07 I'm going to say that I always want my tab width to be 2. I don't want semicolons, so I can take this semi setting and set that to false. I can set single quote to true.

    02:26 With that set up, let's switch back to our index.js file. Let's go back into the terminal. I'm going to run that format command again, npm run format. We'll see that our double quotes have been converted to single quotes, all the semicolons are gone, and it's looking pretty nice.

    02:46 By only changing the files that have been changed since the last commit, pretty-quick speeds up this automatic formatting.

    02:52 In our case, since we've just introduced Prettier and we have all these files, I'd like to automatically format all the JavaScript files once, so any new projects we start from this repository automatically have our default formatting in all the included files.

    03:06 To do that, I'm going to jump back into the terminal, and I'm going to use npx to run Prettier against all the JavaScript files in this project. I'll use npx prettier. I'm going to pass it the write flag so that my changes are automatically written and saved to those files. Then I'm going to specify a file pattern.

    03:25 I'm going to '*/.js' and I'll execute that. If we expand the terminal, we'll see that it's run through, and it's updated bundle files, and our jest-config-app.js, and our test files. Some of these files are generated. We don't necessarily want those included. It doesn't matter that we formatted them this time, but normally, we just don't want to bother with that.

    03:55 I'm going to come in here, and I'm going to add another file to the root of my project. This one is going to be called .prettier-ignore. In the prettier-ignore, I'm going to add dist, and I'll save that. Then I'm going to go back into the terminal. I'm going to run that command again and expand this out.

    04:18 We'll see that none of the files in dist are included this time. It's only files that are part of our project, which is what we want.

    04:25 We can also format our JSON files with Prettier. I'm going to update the prettier-ignore, because I want to format things like my package.json, but I don't want to format the package-lock.json, because that's a generated file. I'm not worried about the format on that.

    04:38 In prettier-ignore, I'm just going to add package-lock.json, save the file, and then back in the terminal, I'm going to go back to that npx prettier command, and I'm going to update my file path to look at JSON files this time. I'll run that. We'll see that it executed against our package.json, but not our package-lock.

    05:06 Now that we have prettier installed and configured, and all of our files are formatted, the other thing we can do is we can set our editor up to automatically format our files for us using our Prettier config.

    05:17 There's Prettier support for a bunch of editors, but I'm using VS Code here. Let's walk through that real quick.

    05:22 If I open up my extensions toolbar here, I can type in Prettier, and there's going to be a lot of options available. I'm going to use this Prettier VS Code extension. You can install and, in my case, I've disabled it for this lesson. I'll enable it, and I'm going to have to reload VS Code to do that.

    05:45 With that installed, let's go into our document. I'm going to add some unnecessary indentation. I'll add a couple of semicolons, since those are turned off in our Prettier config. I'm going to save the file. That's not going to change anything, yet.

    06:01 If I go into my command panel, I can go in and I can run this format document command. That's going to apply my Prettier config to the file, and then I can save those updates. It would be even easier if VS Code would apply my formatting when I save the file.

    06:16 I'm going to go into my VS Code settings. I'm going to use cmd+, to do that. Here, I'm going to search for format. I'm going to find this editor format on save setting. I'm going to check that, and then I can close my settings.

    06:33 I can come in here, and I can mess up my formatting again. I can save the file, and it's going to apply that formatting for me.