<label>Pass:
  <input type=password placeholder="Enter Your Password" /> 
  <i class="fa fa-eye"></i>
</label>

   label{
      position:relative;
    }
    input+i{
      user-select:none;
      cursor:pointer;
      position:absolute;
      right:3px;
      top:2px;
    }  

    document.querySelector('input[type="password"]+i')
      .addEventListener('click', function(){
      let i = this.previousElementSibling
      i.type = i.type=='password' ? 'text': 'password'
      this.classList.toggle('fa-eye-slash' )
    })