Dynamically import a stylesheet depending on the environment

[masaanli]

Please provide us with the following information:

I'm having a question about how to dynamically import 'scss' files based on the environment which is serving or building.

Example.

I have a /styles/app/app-1.scss.
I have a /styles/app/app-2.scss.

Now i have also 2 environments called app-1 and app-2
I want to be able to say if it's served/builded environment is app-2 for example that it's loading the /styles/app/app-2.scss stylesheet.

This so I can develop 1 website and depending on how I build it's including the stylesheet for overwriting some parts of the application, style the application.

OS?

Windows 7, 8 or 10. Linux (which distribution). Mac OSX (Yosemite? El Capitan?)
Mac OSX Sierra

Versions.

Please run ng --version. If there's nothing outputted, please run in a Terminal: node --version and paste the result here:
cli c30 and node v 7.5.0

Repro steps.

Was this an app that wasn't created using the CLI? What change did you do on your code? etc.

The log given by the failure.

Normally this include a stack trace and some more information.

Mention any other details that might be useful.

---

Thanks! We'll be in touch soon.

[agatsoh]

Similarly I want to know how to include .less stylesheet files in an angular2 cli project in the current scheme of things.
It would also be nice if you include in the Wiki in what order are CSS files loaded.

1. From angular-cli.json
2. From styles.css
3. styleUrls array inside the Component.
   Which stylesheets are applied first and which ones last and which stylesheets would override the others ?

[RicardoVaranda]

@agatsoh I believe you already posted the order correctly.

At start up it loads it from styles array in angular-cli.json which is where styles.css is loaded from lastly your specific stylesUrls within your components.

[RicardoVaranda]

@agatsoh @masaanli I have found a solution for this, keep in mind this isn't exactly supported by the cli but rather a feature of Webpack.

Example of app.component.ts:

import {Component, OnInit, isDevMode} from '@angular/core';

@Component({
  selector: 'app-root',
  template: '<h1>Testing :)</h1>',
  styleUrls: ['./app.component.css']
})
export class AppComponent implements OnInit {
  ngOnInit(){
    if(isDevMode()) {
      require("style-loader!./../styles2.css");
    } else {
      require("style-loader!./../styles.css");
    }
  }
}

Where styles2:

h1 {
  color: red;
}

Styles:

h1 {
  color: green;
}

While this may work it was brought to my attention by @filipesilva that there might be some drawbacks to using this solution such as:

• Your code not being as portable
• Styles may not be processed correctly
• Might break if cli changes its loaders

[masaanli]

@RicardoVaranda nice ! Something like this was what I searched for.

But then it's loading a css file. But is there maybe a option to do it when building or serving the project? So it's scss compiled together?

[RicardoVaranda]

@masaanli Similar to how I have stated above

if(isDevMode()) {
      require("style-loader!./../styles2.css");
    } else {
      require("style-loader!./../styles.css");
    }

You can also do:

if(isDevMode()) {
      require("style-loader!./../styles2.scss");
    } else {
      require("style-loader!./../styles.scss");
    }

Where for example styles2.scss is:

$green : green;

h1 {
  color: $green;
}

But once again the same implications I stated above apply.

[masaanli]

@RicardoVaranda

I tested it and it is working!

The problem I discovered is, I use Bootstrap and have in the angular-cli.json my variables defined.

I cannot override them in the app.component (require .scss)

You know maybe a solution for this?

I managed to fix it, but maybe there is abetter solution.

I fixed it by @import everything in that stylesheet.

so i require a stylesheet dynamically in the app.component.ts and in that stylesheet i import the other stylesheets. (so i have double code) for several apps. but it's working.

STILL HAVE THEN THE PROBLEM: That the variables inside the style file for components which are included like 'styleUrl' are not working anymore!!

(because 2 times require will not work. (cannot read variables from the other files).

[RicardoVaranda]

That is because the instance of style-loader is different when called by the cli and when It's called by the require and thus you won't have access to variables from the cli instance and vice versa.

To be honest I think you are over complicating the logic to do this, A better approach for you in my opinion would be to have 2 different styles: styles.scss styles-dev.scss

Inside each of these just do the @import like you mentioned above requiring any other file you need to overwrite. Yes you will have change it in angular cli every time you want to switch between environments but realistically how often are you really switching between both of these.

If you wanted to change environments you would have to turn off the cli and re-run it with the new environment variable anyway with your current setup.

[masaanli]

@RicardoVaranda true, but I have 1 code base and depending on the commando's I wanna be able to say deploy this version or deploy that version. You cannot add logic in the angular-cli json ;) So that's no option for me.

[agatsoh]

@RicardoVaranda Do you have any idea how we import .less stylesheets in angular2 ?

And I apologise I forgot to ask you, what about the stylesheets declared in index.html ? Do they override all other stylesheets? This is what I am observing.

[filipesilva]

Closing as this is now mostly a discussion question instead of an issue.

The CLI doesn't provide you with any preferred way out of the box to dynamically lazy load styles and apply then. You'll have to come up with a strategy yourself. Stack Overflow has great answers for this sort of question.

Functionality that we do have is a way to have a global style that isn't loaded by default in index.html, and instead are just outputted to dist. You can set a global style to be lazy, see https://github.com/angular/angular-cli/blob/master/docs/documentation/stories/global-styles.md for more info. This has actually been around for a while but wasn't documented.

Here are a couple of random web results that show how you apply styles via javascript:

• http://stackoverflow.com/questions/574944/how-to-load-up-css-files-using-javascript
• http://stackoverflow.com/questions/25767089/adding-a-stylesheet-dynamically
• https://www.w3.org/wiki/Dynamic_style_-_manipulating_CSS_with_JavaScript

Approaches that intrinsically depend on webpack loader might work right now but are not officially supported, which means they can stop working at any time or might not work as expected.

[RicardoVaranda]

@agatsoh Depends on where you want to import them and how. If you mean dynamically like what masaanli was trying to achieve you can use the same solution as I posted above I've tested it by refactoring styles2.scss to be styles2.less and the contents to be:

@green : green;

h1 {
  color: @green;
}

This will load correctly but it's prune to the drawbacks I have posted above.

The priority in which it applies the css is as follows:

Component -> angular-cli styles [] -> index.html

This screenshot might clarify it for you:

Blue is the component styles, red is styles.css being loaded from angular-cli.json and finally green is a link tag from index.html.

Hope this clarifies your queries.

[kujma10-zz]

I have used solution from this issue. However when isDevMode is undefined, it loads both scss files. When I console.log it only goes to the second block. Any idea why this happens?

    if(isDevMode()) {
      require("style-loader!./../styles2.scss");
    } else {
      require("style-loader!./../styles.scss");
    }

[yasiryc]

@kujma10 , did you import isDevMode from @angular/core? Also ensure that you are doing development build and not production.