Javien Lee

Posted on Jun 5, 2022 • Updated on Jun 6, 2022

Do you use semicolon in JS?

Do you usually use semicolon when you program? And why?

In my case, I don't use semicolon. I know how ASI(Auto Semicolon Insertion) works and it's rule makes my code more clean and readable.

Let me give you an example. The code below is an incorrect way to use ASI.

let foo = 'bar'
[1, 2].map(e => e + 1)

because ASI will fix the code like this.

let foo = 'bar'[1, 2].map(e => e + 1)

However, most of developer do not write code like this. In that code, we can't figure out what [1, 2] means. So we store it in a variable with name, that everyone can understand.

const ids = [1, 2]
const newIds = ids.map(e => e + 1)

I'm not blaming people for using semicolons in their code, but I don't think there's a particular reason for me to use semicolons. Please share your opinion :p

Top comments (28)

Stephanie Handsteiner • Jun 5 '22

When I join a codebase I use whatever the codebase defines, to keep it consistent within.

As for my own projects, yes, I always use semicolons and have setup my linting config in a way to respect that. I just like my semis! 🙂

FJones • Jun 5 '22

This. Evidently, adapt to the prevalent style in the codebase, and be consistent with it. But I also prefer using them and enforcing them through linting rules. In fact, I'm currently in the process of adding linter rules to the codebase I was just put in charge of, and semicolons are on the list of rules to enable as soon as I have time to resolve the existing inconsistencies.

Javien Lee • Jun 6 '22

It's true linter makes us not fall into conflict😂 And as one of the people who uses semicolons, may I ask why you prefer to use semicolons?

FJones • Jun 6 '22

For a start, semicolons are more readable - they terminate a statement, regardless of indentation confusing things. But also because, for me at least, omitting them takes more thought than just adding them, so it's a timesink, too.

Javien Lee • Jun 5 '22 • Edited

Frankly, it's not a big deal to follow the rules they already use. Thank you 👍

Alex Lohr • Jun 5 '22

Semicolons are part of the standard; use them if you want or don't, but please keep it consistent.

Javien Lee • Jun 5 '22

thank you for sharing your opinion :)

Jan Küster • Jun 5 '22 • Edited

I personally don't use semicolons and also enforce them to be absent, using standard as my linter (precisely standardx to allow a few customized settings).

I already got so used to it that writing with semicolons feels annoying to me.

Javien Lee • Jun 5 '22

100% agree. And it's a good news that I'm not the only one who feels awkward when using semis😂

૮༼⚆︿⚆༽つ • Jun 5 '22

No-semicolon seems a must when writing variable declaration in Elm/Haskell style.

const S = Symbol
    , sData = S()
    , sEffect = /* @__PURE__ */ S()
    , sComponent = /* @__PURE__ */ S()

Changing the order require to remove and add semi-colon if semi-colon is enforced by the linter or formatter.

Carlos Garcia ★ • Jun 6 '22 • Edited

I've always used semicolons. The first time I heard about this new trend of not writing them, to be honest I found it quite dumb, like it made no sense. When I asked for the reasoning behind it on Twitter the only two kind of answers I got were "because they're not necessary" and "it saves you time". I wondered, how many seconds can you save in a day by not writing semicolons?

Then I landed on a project which codebase did not use semicolons. I did not bat an eye to it and just went along with being in a "modern" and "cool" project.

That is, until we got around to define our linting and auto-fix rules, when everyone agreed semicolons should be added on file formatting. What was the point then?

I guess it all comes down to personal preference, but as others have said, consistency is the most important thing.

Randall • Jun 5 '22

I use semicolons. I guess I'm just used to it. It feels weird to me to not use semicolons. For a beginner, or someone who is not already pretty good at JS, I recommend always using semicolons. Otherwise it's only a matter of time until you run into a really confusing error caused by "incorrect" AIS and have to beg for help. No-semicolons is cool and all (I guess?) but learn the language very well first, or you are asking for trouble.

Javien Lee • Jun 6 '22

It can be really confusing for beginners. I think, however, it will be an option to use it after understanding the principles of ASI. 🤗

jzombie • Jun 5 '22 • Edited

I used to care a lot about this, until I started working on a mix of projects w/ and without them, and just leave it up to the linter to fix the changes on save.

With that in mind, I tend to not use them when I know the linter will just do its thing, but if there happens to not be a linter involved I will usually insert them because it feels purer to me.

JoelBonetR 🥇 • Jun 5 '22

I use them, mostly auto inserted by Prettier (format on save).
I feel it more readable for humans as you can find easier where the statements end without extra effort.