一、news.component.ts

import { Component, OnInit } from '@angular/core';
@Component({
  selector: 'app-news',
  templateUrl: './news.component.html',
  styleUrls: ['./news.component.css']
})
export class NewsComponent implements OnInit {
  arr = ["html", "css", "js", "vue"];
  constructor() {}
  ngOnInit(): void {
  }
}

二、news.component.html

<ul>
    <li *ngFor="let item of arr;let key=index;" [ngClass]="{red: key==1,blue:key==2}">{{item}}</li>
</ul>

三、[ngStyle]同理