Writing great Javascript

http://oli.me.uk/2012/03/14/writing-great-javascript

by neya • 14 years ago

76 10 14 years ago

oli.me.uk

I've never seen the preceding semi-colon like that. It makes perfect sense, there are a lot of JavaScript coders these days coming from languages like Ruby and these people often don't use semi-colons, very smart advice to protect against that!

sn0wright• 14 years ago

The preceding semi-colon is definitely a very smart advice. I also will have to try out jshint (I've been using jslint).

pshc• 14 years ago

Adding a leading semicolon just in case seems like overly defensive programming to me. You ought to pick trustworthy tools. If your script concatenator doesn't work right, I think it's better to fail fast rather than let things quietly be half-broken all over the place.

csomar• 14 years ago

You ought to pick trustworthy tools.

Many JavaScript snippets are made to be integrated and added by other people on their websites.

Perceptes• 14 years ago

It doesn't even need to be a semicolon. It's also common to see a ! used for this purpose.

funthree2• 14 years ago

You really only need one or the other depending on the style of the code you are using in the rest of your project.

If you write js using semi-colons everywhere:

    (function () { })(this);

    (function () { })(this);

    (function () { })(this);

If you dont want to use semi-colons unless you have to:

    ;(function () { })(this)

    ;(function () { })(this)

    ;(function () { })(this)

Basically, never start lines with `(` or `[` without semis and don't throw in line breaks liberally without understanding what semicolon insertion is going to happen.

http://blog.izs.me/post/2353458699/an-open-letter-to-javascr...

user242• 14 years ago

But what if you do this:

    <script src='3rdpartyA.js'></script>
    <script src='yourscript.js'></script>
    <script src='3rdpartyB.js'></script>

You need the semicolon at both ends to insulate your script from the unknown coding style or 3rd party scripts which may be appended or prepended to yours.

If 3rd party A omits a trailing semicolon, or 3rd party B doesn't uses your semicolon prefix style then by wrapping your script in semicolons you pre-emptively prevent problems.

I believe this is an example of the wider coding style called "defensive coding".

funthree2• 14 years ago

Or you could actually just read the source code of the libs you are using...

Writing great Javascript

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