Angular 6将Html中的背景颜色设置为CSS变量

Question

I am using Angular 6 and I have a simple div and want to set the background color of this div from inside the template. This works fine when passing normal colors. But this does not work with CSS Variables.

This example works

<div [style.background]="'red'">...</div>

This example does not work

<div [style.background]="'var(--some-css-var)'">...</div>

Answer 1

You have to use ngStyle

<some-element [ngStyle]="{'background-color': styleExp}">...</some-element>

https://angular.io/api/common/NgStyle

Answer 2

In order to bind a style property to a CSS variable in the HTML template, the CSS variable expression var(...) must be sanitized. You can define a custom pipe:

import { Pipe, PipeTransform } from '@angular/core';
import { DomSanitizer, SafeStyle } from '@angular/platform-browser';

@Pipe({
  name: 'safeStyle'
})
export class SafeStylePipe implements PipeTransform {

  constructor(private sanitizer: DomSanitizer) { }

  transform(value: string): SafeStyle {
    return this.sanitizer.bypassSecurityTrustStyle(value);
  }
}

and use it in the HTML template:

<div [style.background-color]="'var(--some-css-var)' | safeStyle"></div>
<div [style.background-color]="bkColor | safeStyle"></div>

bkColor = "var(--some-css-var)";

See this stackblitz for a demo.

Answer 3

You can do it in 2 ways

1. use pipe that get a string and return some color code code.

    <div [style.background-color]="someString | colorSetter"></div> 

2. add to the html tag a dynamic class for example:

   <div class="my-div" [class]="someClassName"></div>

and in the scss add the options

scss:

.my-div{
    &.optoin1{
       background-color:red;
     }
&.optoin2{
       background-color:black;
     }
&.optoin3{
       background-color:green;
     }
&.optoin4{
       background-color:yellow;
     }
}