Preview de imagens antes do upload com Angular

handleFileInputChangeComum.ts

function onChange(event: any) {
  if (!event.target.files[0] || event.target.files[0].length === 0) {
    alert("Nenhum arquivo selecionado");
    return;
  }

  const mimeType = event.target.files[0].type;

  if (mimeType.match(/image\/*/) == null) {
    alert('Apenas imagens são suportados');
    return;
  }

  const reader = new FileReader();
  reader.readAsDataURL(event.target.files[0]);

  reader.onload = (_event) => {
    this.message = "";
    this.imageData = reader.result;
  };
}