application.js 中 require() 和 //= 的区别

Question

In a Rails application, inside application.js, what does the lines that start with //= require mean and what is the difference with a normal require(); ?

I'm new at web development, at the beginning I thought this were irrelevant as they appear as commented.

For example, this:

//= require cocoon
//= require jquery_nested_form
//= require jquery3
//= require jquery_ujs
//= require jquery

Answer 1

Rails uses Asset Pipeline(Sprokets) to bundle all js and css files in one and minifies it for better performance of the page loading.

app/assets/javascripts/application.js called manifest file where you mention your javascript files you want to include and the order in which you want to include using

//= require

Similarly for css, you have app/assets/stylesheets/application.css

/* ...
*= require_self
*= require_tree .
*/

require() in context of ruby is to load other file in current file so that it's functionality can be reused.

require in context of javascritp is to load javascript modules to be used in current context/file. It's CommonJS syntaxt. This comes into picture when you use webpacker gem.