how to display HTML with angular function?

Question

I'd like to display formated HTML using type script function in an angular component, I wanted it to display question from diferent type, I tried this,

import {Component, OnInit} from '@angular/core';
import {TP, Question, Qtype} from "../tp";
import * as Exercice from '../assets/Exercice.json';

@Component({
  selector: 'app-tp',
  templateUrl: './tp.component.html',
  styleUrls: ['./tp.component.css']
})
export class TpComponent implements OnInit {


  constructor() {
  }

  ngOnInit(): void {
  }

  displayQCM(question: Question) {
    return `
      <div>
            <hr class="w-100">
            <h3>Question n°${question.number} ${question.questionType}</h3>
            <p>${question.questionContent}</p>
            ...
            QCM question element
            ...
        </div>
    `;
  }

  displayTrueOrFalse(question: Question) {
    return `
      <div>
            <hr class="w-100">
            <h3>Question n°${question.number} ${question.questionType}</h3>
            <p>${question.questionContent}</p>
            ...
            true or false question element
            ...
        </div>
    `;
  }

  displayQuestion(question: Question) {
    return `
      <div>
            <hr class="w-100">
            <h3>Question n°${question.number} ${question.questionType}</p>
            <p>${question.questionContent}</p>
            ...
            normal question element
            ...
        </div>
    `;
  }
}

<div class="row justify-content-center">
  <div class="col-12 col-lg-6">
    <h2>Questions</h2>
    {{displayQCM()}}
    {{displayQuestion()}}
    {{displayTrueOrFalse()}}
  </div>
</div>

but the HTML display only as plain text writing fully the code on the page, do you know how to fix this ?

EDIT: edited code to be more in the context, the question comes from a json file and there's 3 type of them, I created a function to translate them into Question and depending on there type I want 3 way to display them in 3 different forms, each type as a long HTML development and are displayed with different tag and element

Answer 1

You need to use [innerHTML] property in your html file

<div class="row justify-content-center">
  <div class="col-12 col-lg-6">
    <h2>Questions</h2>
   <div [innerHTML]="displayQCM()"></div> 
    <div [innerHTML]="displayQuestion()"></div>
    <div [innerHTML]="displayTrueOrFalse()"></div>
  </div>
</div>

Answer 2

If you are just trying to inject dynamic content you need to sanitize your html string and then use innerHtml. From your question Im not sure what the goal is and there must be a better way without injecting Html but you would need to clarify the goal.

questions: Array<SafeHtml> = new Array<SafeHtml>();
myJson: Array<string> = []; //I dont know where its coming from

  constructor(private sanitizer: DomSanitizer) {
  }

  ngOnInit(): void {
      myJson.forEach((question) => { 
          this.questions.push(this.sanitizer.sanitize(question)); 
      })
  }

  <div class="row justify-content-center">
    <div class="col-12 col-lg-6">
      <h2>Questions</h2>
      <div *ngFor="let q of questions" [innerHtml]="q"></div>
    </div>
  </div>