remove duplicate content

[lfender6445]

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[hshoff]

Hi @lfender6445 thanks for checking out the guide!

I can see how that might look like a duplicate, but there's actually a subtle difference between the two. The second one is prefixed with a ;. This prevents a problem that can occur when concatenating js files.

Let's assume all of the js files follow the IIFE pattern like so:

(function() { console.log('code'); })();

When concatenating a few files together you get something like this:

(function() { console.log('file1'); })();
(function() { console.log('file2'); })();
(function() { console.log('file3'); })();

> file1
> file2
> file3

This is works great. But now let's say file2.js doesn't follow the same style you do and avoids semicolons. You get something like this:

(function() { console.log('file1'); })();
(function() { console.log('file2') })()
(function() { console.log('file3'); })();

> file1
> file2
> TypeError: undefined is not a function

Oh no! With a missing semicolon it tries to invoke whatever was returned from file2.js which in this case is undefined.

A way to safeguard yourself from this is to prefix your IIFE with a semicolon

;(function() { console.log('file1'); })();
(function() { console.log('file2') })()
;(function() { console.log('file3'); })();

> file1
> file2
> file3

Another way to do this and is our preferred modules style (see Modules):

!function() { console.log('file1'); }();
(function() { console.log('file2') })()
!function() { console.log('file3'); }();

> file1
> file2
> file3

For a full explanation on why this happens see here: #44 (comment) & #21 (comment)

🍻