Meaning of - "//= require angular/angular" - javascript

I have a similar problem of using Angular with Grails, pls. refer this question that already gives all the details/solutions/answers: How to integrate angular js into grails 2.3.4?
In the answers to this question, people have given good answers, but they are talking about ....
"require the module on screen"
... & sample code (?) fragments like these:
//= require angular/angular.js
//= require_tree views
//= require_self
What is the meaning of "requiring" the module ("resource bundles": as given in the first answer), & other/above code fragments, or whatever they are.
Does it means normal require statements:
require(['angular']);
etc.?
Things are not very clear.

In a Ruby on Rails application you would use manifest files to include all your dependencies. That is a code snippet from the application.js (default) manifest file where it's including javascript files or paths using the "//=" javascript include syntax.

Grails uses different resource mangement plugins for javascript files, css, images, etc.. Code you mentioned
//= require angular/angular.js
//= require_tree views
//= require_self
is from grails asset-pipeline plugin.
Resource bundles term used in grails resources plugin where you declare bundles in ApplicationResource.groovy file.
When you want set of js or css file to be included in a page you just need to include manifest file (for assest pipeline) or require module (for resources).
Both plugin have good documentation to refer.

//= require angular/angular.js
Is simply rails syntax for requiring and registering dependencies to your rails applications. Although your question is a little vague if you are trying "require an angular module" than you must list it as a dependency when you declare your angular module. This is totally unrelated to rails but will look something like this:
angular.module('myApp', ['ngRoute', 'ngTouch',])
where the items inside the array (ngRoute, ngTouch) are other modules that become depencies of 'myApp'.
This page should help!

Related

Why do we have to require the JS files inside application.js in rails?

I am new to rails so pardon the question. Now, why do we have to require the JS files inside the application.js file or the css files inside the application.css file? As far as I have read that when we launch the server rails loads all the javascript and css files from the directory into one file, so if it already loads all the files from the directory why there is a need to write inside the application.js or application.css file?
For example:
//= require abc
//= require xyz
If I already have abc.js and xyz.js file, why should I require them inside application.js file?
You are misunderstanding the concept. Let me explain the process. As you know, when you launch the server, rails first precompiles the files inside the assets folder with the help of sprockets-rails gem, but it does so by following the directives specified inside the manifest files i.e application.js and application.css.
Now inside the application.js you have "//= require_tree .", this tells sprockets to load all the files inside the javascript directory, process them, compress and combine them to produce one master Javascript file, this helps to reduce the page load time of the website. Now,here is your question, since "//= require_tree ." directive already takes all the javascript files present inside the javascript directory, why there is a need to specify the javascript files inside application.js? The answer is "Order".
"//= require_tree ." it loads, compress and combine all the JS files in an unspecified order or random order. Now, if you are a web developer or have started now, you might know or will come to know that many times you have to load JS files in some specific order, otherwise there may arise some conflict when we implement them, they might not work as we want them to.
One such famous combo is jquery and bootstrap. In order to use bootstrap JS part it needs jQuery, so you have to initialise jquery first and then bootstrap. Precisely for this reason in rails you require the files inside application.js specifying the order in which you want the sprockets to load,compress and combine into one master JS file. As sprockets processess the directives from top to bottom in the order specified in the application.js file, it becomes important to require the files in application.js file. If you have 2 javascript or css files which in no way connflict with each other then, there is no need for you to require the files inside application.js or application.css file and they will still work fine.
For example:
//= require jquery
//= require jquery_ujs
//= require bootstrap.min
//= require_tree .
Above, the sprockets-rails gem will first load jquery.js file then jquery_ujs.js file and then bootstrap.min.js file in that order. There is no need to add the extension as it assumes that all the files will be of type javascript only.
The above whole explanation also applies for the precompilation of css files specified inside application.css.
For more information, I advise you to visit http://guides.rubyonrails.org/asset_pipeline.html and read about rails asset pipeline.

How are Sprockets directives read in manifest file when using Rails?

New to Rails so bear with me...I was looking at a manifest file (application.js) today while researching the asset pipeline and was curious how the directives such as //= require jquery are being read. Is this something Sprockets is doing in the background? How? Why must the directive be commented out first, and the equal sign added? If I uncomment the directives and load the application.js file in my broswer, I no longer see the jquery library contents. Just curious how this is working in the background.
Also, when I add my own custom css stylesheet, do I add a require directive in the application.css manifest file, or do I add the stylesheet link such as <link rel="stylesheet" type="text/css" href="mystyle.css">? Or do I do both? I'm assuming I shouldn't add css directly inside of the manifest file...
Thanks!
Dont know how much you know, so will try to explain in details.
Rails stores our assets (like images, css, js files) in separate places, so its all in order and better for us - devs, to use. So thats called Assed Pipeline. When Rails loads those assets, say, css files, it creates one big file from all our app files, to avoid multiple calls. And Manifest is like a map or rules for Rails which files to include in that big css file and this *= is whats telling Rails what exactly to include (I consider it as a Rails syntax). So when you have something like this:
//= require jquery
//= require jquery_ujs
//= require turbolinks
//= require_tree .
require_tree . tells Rails to grab all files from the javascripts folder, while //= require jqueryand others directs Rails to special cases - assets, usually used by your gems (those files you never keep in your javascripts/stylesheets folders, so //= require_tree . cant see them).
When you add your on css file, you just add it in the stylesheets folder and require_tree informs Rails to include it in the big picture. But Rails has a nice feature - scaffolding. You scaffold your object with command rails g scaffold User and Rails creates everything for you - views, controller, model, tests (and who knows what else :) ). So in this case you don't even need to create your css file, just insert css rules into it and Rails will find it due require_tree .
A bit different story with sass files:
If you want to use multiple Sass files, you should generally use the
Sass #import rule instead of these Sprockets directives. When using
Sprockets directives, Sass files exist within their own scope, making
variables or mixins only available within the document they were
defined in.
So if you will be using Bootstrap (probably will), this is a important to know as well.
Hope this helps
How? Why must the directive be commented out first
Because this is sprockets directive. It is executed well before any js/coffee in that file gets the chance to run. And css is not "runnable" code at all. How do you make this kind of code not produce any errors? You comment it.
... and the equal sign added?
To tell these special directives apart from other, "regular" comments, which may be in that file.
I'm assuming I shouldn't add css directly inside of the manifest file...
Why not, go ahead. Although you may want to put any custom code in separate files for reasons of code organization. But technically, there's no problem here.
Also, when I add my own custom css stylesheet, do I add a require directive in the application.css manifest file
No need, require_tree . will find and include your file.
or do I add the stylesheet link such as <link rel="stylesheet"type="text/css" href="mystyle.css">?
Nope, don't do that.

Properly requiring three.js in Rails

I tried searching for a solution for this, but unfortunately nothing useful I could find came back.
I'm currently building a new Ruby on Rails application and attempting to include three.js to start practicing using it. In order to test if it was successfully required I'm using my browser console, but receiving the error:
ReferenceError: THREE is not defined
From what I saw on this question: Most efficient way to get a Three.js project to work in a ruby on rails app?
I should be receiving a return value.
I've tried both adding the three.js file in the assets/javascripts folder and using the threejs-rails gem here: https://github.com/marvindanig/threejs-rails with no success.
I've made sure to require it in the asset pipeline in the application.js file:
//
//= require three
//= require jquery
//= require jquery_ujs
//= require turbolinks
//= require_tree .
Does anyone have recommendations on what I should try next? My main issue right now appears that it's not being required correctly.
EDITED: Problem was solved. Turns out I was inheriting from the wrong controller model.
Take the Three.js file and drop it in your assets/javascript folder.
In your application.js make sure you have at the end "//= require_tree ." and it should be working fine. You should remove the "//= require three" line because rails loads it automatically and you shouldn't load anything before jquery and turbolinks or else things won't load correctly. If you want to add it to your project explicitly, add it at the end just before "//=require_tree ."
a.) Include your three.js file in
"app/assets/javascripts/three.js"
b.) in application.js file write #= require three
Make Sure server should be running. refresh the web page and type in web console(F12): Three, If it gives return result. it's done.

Spree - cannot override js.coffee file

Simply followed instructions from http://guides.spreecommerce.com/developer/asset.html but it just doesn't work. New js files are included and loaded, but if I create file with the same name say product.js.coffee original file is loaded anyway. Any suggestions?
All.js
//= require jquery
//= require jquery_ujs
//= require spree/frontend
//= require_tree .
I've been tearing my hair out over this problem all morning.
In the end what worked for me is to specify every single file I wanted to overwrite in /app/assets/javascripts/spree/frontend/all.js.
E.g., if you want to overwrite cart.js.coffee and checkout/address.js.coffee, your all.js should look like:
//= require jquery
//= require jquery_ujs
//
//= require spree/frontend
//= require spree/frontend/cart
//= require spree/frontend/checkout/address
//
//= require_tree .
Don't ask me why that's necessary. My understanding is that //= require_tree . should do that automatically, but it my case, well, it wasn't.
After creating an all.js file and redundantly specifying each file, this finally worked for me. But I'm a spree/rails noob, so there's quite probably a better solution.
Edit:
Actually, to get this working I had to put the above in /vendor/assets/javascripts/spree/frontend/all.js and remove /app/assets/javascripts/spree/frontend/all.js. Still confused why this is necessary and why require_tree doesn't pick these up automatically, but happy to finally get it working.
Backporting this patch for Solidus 2.1.0 solved my issue of replacing/overwriting JS assets [1].
The problem appeared to be that there was an issue with Sprockets where using require_tree or relative require prevented JS assets in the pipeline from being overridden.
In summary
Create a new file under your project's vendor/assets with the same filename as the JS file you're going to replace in Solidus. For example, to overwrite the file solidus_backend/app/assets/javascripts/spree/backend/flash.coffee, create a replacement file in your project at your_project/{app,vendor}/assets/javascripts/spree/backend/flash.coffee. [2]
Create the files your_project/{app,vendor}/assets/javascripts/spree/backend.js and your_project/{app,vendor}/assets/javascripts/spree/backend/templates/index.js in your project.
Copy the contents for the backend.js and index.js files from solidusio/solidus#1613 into your project.
Remove any requires for files that do not exist in your Solidus version, and keep any custom requires if you already had backend.js and index.js defined. [3]
Footnotes
Includes .js, .coffee, .hbs, and any other files that compile to JavaScript during the asset pipeline compilation.
Either directory between {app,vendor}/assets in your project will work since they should both be in the asset pipeline loadpath. It's a matter of preference how you want to organise Solidus extensions and overrides.
I had to remove spree/backend/images/upload from backend.js
and spree/backend/templates/products/upload_progress from index.js since I was using an older version of Solidus and those files didn't exist yet, so I would get an FileNotFound error from Sprockets.

Ruby on Rails - how require is executed in application.js

I am reading a book for "Ruby on Rails". In the "application.js", we are including other JavaScript libraries in the following way and more specific - jQuery UI:
//= require jquery
//= require jquery_ujs
//= require jquery-ui
As this is ordinary JavaScript file (not ruby extensions here like "html.erb" for exmaple) how the application knows to execute the require command? What kind of JavaScript syntax is this:
//=
and as this is ordinary JavaScript file, why we are not using "script" tags to include JavaScript files?
Also, I have read here that "require" method will check for this library in define by $LOAD_PATH variable folders. How can I see where the "jquery-ui" is stored? I am asking because in other applications in order to use jQuery UI I should add not only JavaScript file, but css file and images used by the library - in this case, we are doing this only with single line?
What kind of JavaScript syntax is this.
Anything starting with a // is a Javascript comment.
How is it able to process it ?
Sprockets on the server side scans the JS file for directives. //= is a special Sprocket directive. When it encounters that directive it asks the Directive Processor to process the command, require in this example. In the absence of Sprockets the //= require .. line would be a simple JS comment.
Ruby require vs Sprockets require
These are two completely different things. The one you link to is Ruby's require.
Why not use script tags to load JS files.
Usually, you want to concatenate all your app JS files and then minify them into 1 master JS file and then include that. I recommend reading the YSlow best practices on this.
I also recommend watching the Railscasts on Asset Pipline - http://railscasts.com/episodes/279-understanding-the-asset-pipeline
Cheers!

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