The idea of this post is not go dive in this subject, but only say that there are other options besides the CSS.

CSS and Preprocessors

The CSS is responsible for the layout or the presentation of your HTML page, describing how the pages will be an exhibit and how their elements will be displayed.

CSS stands for Cascading Style Sheets.

The CSS can be:

  • inline (directly on the component code),
  • internal (inside the tag 'style' in the page) or
  • external (external file with .css extension).

As soon you start to work with CSS you will note that there is a huge chance to repeat the code. To make the CSS build more dynamic, there are the preprocessors. The examples of preprocessors are LESS and SASS.

These preprocessors are compiled to the CSS and used on the client or server. They allow, for example, the use of mixins (template) and variables. Both allow a clean and dynamic CSS. However, SASS is based in Ruby and LESS uses JavaScript.

Some differences between LESS and SASS you can see [1] and [2].

LESS vs SASS

Tutorial LESS Tutorial SASS

Migration to Angular 6

If you need to migrate version you should have pay attention to some points:

You should config your angular.json to accept the processor.

"schematics": {
   "@schematics/angular:component":{
      "styleext":"less"
   }
},

You should declare your less globally or by component.

COMPONENT:
styleUrls: ['../styles/yourstyle.less']
GLOBAL: angular.json
"styles": ["src/yourstyle.less"]

Conclusion

You can choose any of the options, even continue to use CSS. It depends on the objective and maturity of your code and developers.

How I said,  this post is just to say that exists more life than the CSS.

References