title: How to set style for an element in typescript?(Angular)
body: <p>How can I set the background colour for an item within an if statement in typescript? I used <code>querySelector</code> but the answer can use anything to achieve the result.</p>
  
  <p>The selector is <code>(.mat-step:nth-child(2) .mat-step-header .mat-step-icon-selected)</code>.</p>
  
  <p>Here is the code in a <a href="https://stackblitz.com/edit/angular-pujfgf?file=src%2Fapp%2Fapp.component.ts" rel="nofollow noreferrer">stackblitz</a>. </p>
  
  <p>I would appreciate any help!</p>