dynamic class binding not working in angular 9

Question

I need to display dynamic color for a div based on some condition. I am getting console error.

I have tried

<div [ngClass]="{'clr-{{students.rollNo+1}}': students.active}"></div>

students is my array, i have a class called .clr-5, clr-6 etc... in css

Answer 1

string interpolation not work inside property binding. you should deal with that like:

<div [ngClass]="{`clr-${students.rollNo+1}`: students.active}"></div>

Answer 2

try this:

<div [ngClass]="[ students.active ? 'clr-'+students.rollNo+1 : '']"></div>

class bindings are updated in Angular 9. Read more about it here