Just like we use gems on the server, we use third party JavaScript libraries in the browser. These typically provide functionality like:

• General support libraries like jQuery or lodash
• Wysiwyg HTML editors
• Datepickers
• Sliders
• Tooltips
• Dialogs
• …

Choosing and installing a JavaScript library

Take a look at the popular lodash library.

• Try to understand what it does.
• Lodash comes in two variants "Core build" and "Full build". Why is that? Why would you always prefer the "Core build" if sufficient?
• Why does it mention "x kB gzipped"? How is that important?
• Try to add lodash to MovieDB by simply downloading it and adding it to the asset pipeline.
  Where is a good place to put it?
  Can you find a way to make use of it?
• Read about how we manage vendor libraries
• Lodash also provides "CDN copies". What is a CDN? Why do you think we don't use them?
• Lodash can also be installed via "npm". What is that? Why doesn't that work for the Rails Asset Pipeline?
• Often, JavaScript libraries come in "minified" versions. What does that mean? Is it important?

Exercise: Add a datepicker

In your MovieDB, add a "release date" field. Use the Rome date picker to add a UI. Remember to use unobtrusive JavaScript.