Managing CSS in Angular App for Cross Browsers and OS

Do you want to organize your css files in your angular app? Do you want to find out the strategy to segregate the CSS based on cross browsers and operating systems? You CSS designer should not be worried how to manage these. As a developer you should setup your angular app such that it works out of the box.

Introduction

I will use angular 10 project. Then I will install ngx-device-detector node package and finally I will demonstrate the best practice to follow to dynamically load cross browser and operating system related CSS files in your angular application.

Installing ngx-device-detector Angular Library

I am assuming that you have created one angular project named as manage-css using angular cli ng new manage-css --styles=scss. I have angular project created with sass styles.

npm i -S ngx-device-detector

Showing OS and Browser Info using ngx-device-detector Angular Library

Add below code in app component to see how ngx-device-detector works.

app.component.ts

import { Component } from '@angular/core';
import { DeviceDetectorService, DeviceInfo } from 'ngx-device-detector';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.scss'],
})
export class AppComponent {
  title = 'manage-css';
  deviceInfo: DeviceInfo;
  constructor(private deviceDetectorService: DeviceDetectorService) {
    this.deviceInfo = this.deviceDetectorService.getDeviceInfo();
  }
}

app.component.html

<div>
  <ul>
    <li>user Agent - {{deviceInfo.userAgent}}</li>
    <li>Os - {{deviceInfo.os}}</li>
    <li>browser - {{deviceInfo.browser}}</li>
    <li>device - {{deviceInfo.device}}</li>
    <li>os_version - {{deviceInfo.os_version}}</li>
    <li>browser_version - {{deviceInfo.browser_version}}</li>
    <li>deviceType - {{deviceInfo.deviceType}}</li>
    <li>orientation - {{deviceInfo.orientation}}</li>
  </ul>
</div>

Adding default style.scss for all Browsers (IE & Chrome etc.)

styles.scss would be our default style file. You could imagine this is our base style file.

#test {
  background-color: aqua;
  height: auto;
  width: 200px;
}

Let's crate a div in app.component.html

<div id="test">
  This is angular app
  <br>
  Chrome color: aqua
  <br>
  IE color: yellow
</div>

Now our site is running both in chrome and IE browser nicely

Chrome:

IE browser:

Now I have requirement to show border only on IE browser not in Chrome.

Adding IE Browser specific CSS Files in Angular App

Let's assume we are writing CSS for chrome browser as default.
And we want to extend few style class for IE browser.
So lets create styles-ie.scss and extend one of our default class test from styles.scss.

extended test class and added border

@import "./styles.scss";

#test {
  // @extend .test;
  border: 5px red dashed;
}

We need to add this file in angular.json so that angular will add this to the index.html file when we serve or build.

Go to angular.json > architect > build > options > styles and add below code

 "styles": [
              { "input": "src/styles.scss", "bundleName": "styles" },
              { "input": "src/styles-ie.scss", "bundleName": "styles-ie" }
            ],

Now lest run npm run build Notice we have 2 files styles.css and styles-ie.css in dist/manage-css folder

Now in the Index.hml you see Angular build add both CSS files.

We do not want that. Because, I want IE style files to be removed while running in Chrome.

Loading only Chrome Styles on Chrome Browser

Now, I will use deviceInfo object to determine which browser I am in. Then I will use Document from @angular/common to remove the IE specific style files.

In order to do above I will prefer to create angular service StyleService and execute this when my application initialized.

Creating Style Service and Remove IE Specific style files

Lets search all the link nodes with having style files ending with -ie.css and remove them.

Create style.service.ts add below code:

import { DOCUMENT } from '@angular/common';
import { Inject, Injectable } from '@angular/core';
import { DeviceDetectorService, DeviceInfo } from 'ngx-device-detector';

@Injectable({ providedIn: 'root' })
export class StyleService {
  deviceInfo: DeviceInfo;
  constructor(
    private readonly deviceDetectorService: DeviceDetectorService,
    @Inject(DOCUMENT) private readonly document: any
  ) {}

  execute() {
    this.removeIEStylesIfRunningInChrome();
  }

  private removeIEStylesIfRunningInChrome() {
    this.deviceInfo = this.deviceDetectorService.getDeviceInfo();
    const head = this.document.getElementsByTagName('head')[0];
    if (this.deviceInfo.browser === 'Chrome') {
      [...(this.document.querySelectorAll('link') as any)]
        .filter((x) => x.href?.indexOf('-ie.css') > -1)
        .forEach((f) => head.removeChild(f));
    }
  }
}

Create init-styles.ts

import { StyleService } from './style.service';

export function initStyles(styleService: StyleService) {
  return () => {
    styleService.execute();
  };
}

In app.module.ts add provider to call initStyles

 providers: [
    {
      provide: APP_INITIALIZER,
      useFactory: initStyles,
      deps: [StyleService],
      multi: true,
    },
  ],

Showing Chrome and IE specific styles only

Now lets run ng serve

and in Chrome IE specific styles are removed only Chrome Styles are loaded 🙂

and IE browser has extra style file for IE browser specific styles-ie.css 🙂

Adding Operating system specific styles in Angular app

I want to add styles-mac.scss and add black border to be shown only on MAC.

Add styles-mac.scss

@import "./styles.scss";

#test {
  // @extend .test;
  border: 5px black dashed;
}

Update angular.json to add MAC sass files.

   "styles": [
              { "input": "src/styles.scss", "bundleName": "styles" },
              { "input": "src/styles-ie.scss", "bundleName": "styles-ie" },
              { "input": "src/styles-mac.scss", "bundleName": "styles-mac" }
            ],

Update the styles.service to add new method to remove MAC styles if running on Windows OS and call on execute function.

execute() {
    this.removeIEStylesIfRunningInChrome();
    this.removeMacStylesIfRunningInWindowsOS();
}
private removeMacStylesIfRunningInWindowsOS() {
    this.deviceInfo = this.deviceDetectorService.getDeviceInfo();
    const head = this.document.getElementsByTagName('head')[0];
    if (this.deviceInfo.os === 'Windows') {
      [...(this.document.querySelectorAll('link') as any)]
        .filter((x) => x.href?.indexOf('-mac.css') > -1)
        .forEach((f) => head.removeChild(f));
    }
  }

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