a tag as button bootstrap code example

Example 1: bootstrap Buttons

Bootstrap includes several predefined button styles, each serving its own
semantic purpose, with a few extras thrown in for more control.
Using color to add meaning only provides a visual indication, which will
not be conveyed to users of assistive technologies – such as screen readers. 
Ensure that information denoted by the color is either obvious from the 
content itself (e.g. the visible text), or is included through alternative
means, such as additional text hidden with the .sr-only class.

<button type="button" class="btn btn-primary">Primary</button>
<button type="button" class="btn btn-secondary">Secondary</button>
<button type="button" class="btn btn-success">Success</button>
<button type="button" class="btn btn-danger">Danger</button>
<button type="button" class="btn btn-warning">Warning</button>
<button type="button" class="btn btn-info">Info</button>
<button type="button" class="btn btn-light">Light</button>
<button type="button" class="btn btn-dark">Dark</button>

<button type="button" class="btn btn-link">Link</button>

Example 2: bootstrap button outline

<button type="button" class="btn btn-outline-primary" href="#">Primary</button>

Example 3: bootstrap buttons

<button type="button" class="btn btn-primary">Blue</button>
<button type="button" class="btn btn-secondary">Grey</button>
<button type="button" class="btn btn-success">Green</button>
<button type="button" class="btn btn-danger">Red</button>
<button type="button" class="btn btn-warning">Orange</button>
<button type="button" class="btn btn-info">Navy Blue</button>
<button type="button" class="btn btn-light">Light Grey</button>
<button type="button" class="btn btn-dark">Black</button>

<button type="button" class="btn btn-link">Link</button>