title: Angular and text-mask: Regex to validate an input without special characters
body: <p>I have angular 5 with "angular2-text-mask": "^8.0.4"
  <a href="https://github.com/text-mask/text-mask/tree/master/angular2" rel="noreferrer">https://github.com/text-mask/text-mask/tree/master/angular2</a></p>
  
  <p>What I'm trying to do is preventing users entering special characters, except for  -, _, ', which should be allowed for a <code>name type="text"</code> input.</p>
  
  <p>This works for phone numbers:</p>
  
  <pre><code>&lt;input [textMask]="{mask: mask}" [(ngModel)]="myModel" type="text"/&gt;
  
  public myModel = ''
  
  public mask = ['(', /[1-9]/, /\d/, /\d/, ')', ' ', /\d/, /\d/, /\d/, '-', /\d/, /\d/, /\d/, /\d/]
  </code></pre>
  
  <p>But when I try <code>public mask = [/^[a-zA-Z]+$/];</code> which is supposed to accept multiple letters, however I can only write one. What's wrong?
  I like to be able to enter unlimited letters, digits and -, _, '</p>
  
  <p>I tested my mask at <a href="https://regex101.com/" rel="noreferrer">https://regex101.com/</a></p>
  
  <p>Any help is appreciated.</p>