In our code, we get to use import statements with relative paths,
ES6 classes: everything we're used to.
It's business as usual.
Except, how can we use third-party packages?
As we saw earlier, we could import things via a full URL, like import _ from,
and I'll paste in the CDN URL that we used earlier.
With that done, the rest is normal: add _.camelCase() to the log.
If we refresh and check the console...
that works.
But I don't like it!
I don't want to have to include this crazy URL everywhere I use lodash.
And what happens if we upgrade lodash...
and I need to change the URL in 10 different files?
Lame! If we were using a build system, like Webpack, we could just say: yarn add lodash
or npm install lodash We're not using yarn or npm, but we can do nearly the same thing.
Over in the terminal, open a new tab, and run php bin/console importmap:require followed
by the name of the NPM package we want: lodash: Done!
It added lodash to importmap.php and tells us we can use the package as usual.
This means we can say import _ from 'lodash'...
and everything will work fine.
How? When we ran the command, it made one tiny change: it added this section to importmap.php.
And as cool as this is, it's not magic.
Behind the scenes, the command went to the JSDelivr CDN, found the latest version
of lodash, then added the lodash key set to that URL.
If you head over and look at the page source...
no surprise!
We have a new lodash entry inside the importmap!
When our browser sees import _ from 'lodash', it looks inside the importmap for lodash,
finds this URL, and downloads it from there.
Our browser is the hero!
One bummer is that we don't get autocompletion in our editor.
It says "Module not installed".
And if I say _....
it doesn't really work.
It's autocompleting camelCase...
but only because I'm using that down here.
I hope this will be better-supported in PhpStorm soon.
There is a workaround, but it's a bit manual.
Copy the package, go into base.html.twig and add a temporary <script> tag that points to this.
Hit "alt" + "enter" and select "Download library".
This downloads that into the "External Libraries" section down here: /lodash.
Ok, remove that script tag.
Back in app.js, it's still going to underline the import as if it doesn't know what it is,
but it does autocomplete when we use _. something.
For example, tail() is from lodash.
What about updating the versions of packages inside importmap?
Whelp, there's a command for that!
php bin/console importmap:update That will loop through every package
and update its URL to the latest version.
This is already the latest version...
but if we change it to .19...
then run the update command...
it moves back up to .21.
The command could be more flexible - like by allowing you to update just one package,
or by having some version constraints - and those things may be added in the future.
Finally, if you don't want to rely on the CDN, you don't have to.
To avoid it, when you require the package - or any time later - pass the --
download option: In importmap.php, this still shows the source URL to the CDN,
but it downloaded that file into an assets/vendor/ directory.
This downloaded_to points to the logical path for that file.
The result?
When we go over and refresh....
and "View Page Source"...
the importmap now points to the local file!
We're no longer relying on the CDN.
But... now what?
Do we commit this vendor/lodash.js file?
The answer is...
yes. At least at this moment, that's the only way to version
that file and keep it in your repository.
So even without npm or yarn, we can use any npm package we want.
Woo! But sometimes, instead of importing an entire package,
we may only want to import a specific file.
Let's talk about how we can do that next.