18F/web-design-standards

<div class="usa-input-masking">
  <h3 class="site-preview-heading">Alphanumeric Input Mask</h3>
  <label class="usa-label" for="zip">Alphanumeric example</label>
  <div class="usa-hint" id="alphanumericHint">For example, A1B 2C3</div>
  <span class="usa-input-mask" data-mask="___ ___">
    <span class="usa-input-mask--content test" aria-hidden="true" id="alphanumericMask"
      >___ ___</span
    >
    <input
      id="alphanumeric"
      type="text"
      inputmode="text"
      name="alphanumeric"
      pattern="\w\d\w \d\w\d"
      class="usa-input usa-masked"
      aria-describedby="alphanumericHint"
      maxlength="10"
      data-placeholder="___ ___"
      data-charset="A#A #A#"
    />
  </span>
</div>