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We are making an Angular2 application and we want to be able to somehow create a global CSS variable (and update the properties' values whenever changed when the variable is assigned).

We had used Polymer for a while (now we are switching to Angular2 components) and we had used CSS properties (Polymer has some polyfill) and we had just update styles using Polymer.updateStyles().

Is there any way how we can achieve a similar function?

EDIT:

We want something similar to Sass color: $g-main-color or to CSS custom properties color: var(--g-main-color) and whenever we decide to change the value of the property, e.g. something like updateVariable('g-main-color', '#112a4f') it dynamicly update the value everywhere. All that while an app is running.

EDIT 2:

I want to use some global CSS variables in different parts (host, child element...) of my CSS and be able to change the value immediately - so if I change my-color variable, it changes everywhere in app.

I will use Sass syntax for example:

:host { border: 2px solid $my-color }
:host .some-label { color: $my-color }

Is possible to use something like Angular pipes? (But it supposedly only works in HTML)

:host { border: 2px solid {{ 'my-color' | cssvariable }} }
:host .some-label { color: {{ 'my-color' | cssvariable }} }
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1  
I'm interested to know what approach you took. We are having similar requirements. – Yousuf Nov 1 at 23:41
    
I still have no solution for this. Only resonable today approach is probably use of CSS variables with some kind of polyfill... – HoBi Nov 2 at 7:35
    
Do you know of any polyfill that can be used in angular2 to replace variables? – Yousuf Nov 2 at 14:12
    
Nope. :( But you can google some solution, probably. – HoBi Nov 2 at 17:16

1) Using inline styles

<div [style.color]="myDynamicColor">

2) Use multiple CSS classes mapping to what you want and switch classes like:

 /* CSS */
 .theme { /* any shared styles */ }
 .theme.blue { color: blue; }
 .theme.red { color: red; }

 /* Template */
 <div class="theme" [ngClass]="{blue: isBlue, red: isRed}">
 <div class="theme" [class.blue]="isBlue">

Code samples from: https://angular.io/cheatsheet

More info on ngClass directive : https://angular.io/docs/ts/latest/api/common/index/NgClass-directive.html

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1  
This may works, but there is one issue - you have to separate dynamic styles from CSS file, which is never the best way. :( I rather would like to have something inside CSS, but I will have to probably deal with it. – HoBi Nov 7 '15 at 21:43
    
I don't understand. Use SASS/LESS. For dynamic styles from JavaScript I can only see those. Anyway you can't mix static and dynamic styles unless you are doing it wrong. Static: css. Dynamic: JavaScript. – Gerard Sans Nov 7 '15 at 21:45
    
I did say that it would be nice to have something like Angular2 pipes - the ability to write it inside the CSS file or area. But it probably is not possible, so I will have to make it like you had wrote in 1) and maybe just add comment into Sass file, that there is used (or should be) global variable from outside. – HoBi Nov 7 '15 at 21:55
    
If you are feeling adventurous you could build a step to take SASS and output a JS module that you can import ^_^ – Gerard Sans Nov 7 '15 at 21:58

You don't have any example code but I assume you want to do something like this?

@View({
directives: [NgClass],
styles: [`
    .${TodoModel.COMPLETED}  {
        text-decoration: line-through;
    }
    .${TodoModel.STARTED} {
        color: green;
    }
`],
template: `<div>
                <span [ng-class]="todo.status" >{{todo.title}}</span>
                <button (click)="todo.toggle()" >Toggle status</button>
            </div>`
})

You assign ng-class to a variable which is dynamic (a property of a model called TodoModel as you can guess).

todo.toggle() is changing the value of todo.status and there for the class of the input is changing.

This is an example for class name but actually you could do the same think for css properties.

I hope this is what you meant.

This example is taken for the great egghead tutorial here.

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1  
That is not what we want. We want something like in Sass color: $g-main-color or in CSS custom properties color: var(--g-main-color) and whenever we decide to change value of the property, e.g. something like JS updateVariable('g-main-color', '#112a4f') it dynamicly update the value everywhere. All that while an app is running. – HoBi Oct 25 '15 at 11:43

I did this plunker to explore one way to do what you want.

Here I get mystyle from the parent component but you can get it from a service.

import {Component, View} from 'angular2/angular2'

@Component({
  selector: '[my-person]',
  inputs: [
    'name',
    'mystyle: customstyle'
  ],
  host: {
    '[style.backgroundColor]': 'mystyle.backgroundColor'
  }
})
@View({
  template: `My Person Component: {{ name }}`
})
export class Person {}
share|improve this answer
    
I have to be able change styles of either host and child elements which I can not with your solution plus it is kind of messy write styles from outside of "CSS area". Take look to EDIT 2. Btw. instead of taking color from input via an attribute it would be better just import some class and use a variable from it, because I want global variables for whole app. ;) – HoBi Oct 27 '15 at 23:08

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