<button onclick='fn(this)'>&#x1f601;</button>
<button onclick='fn(this)'>&#x1f602;</button>
<button onclick='fn(this)'>&#x1f603;</button>
<br/>
<input type='text' id='sample'>
<hr/>

<a href='https://modx-gu.ru/html-codes/emoji'> коды </a>

function fn(e){
  
  let sample = document.getElementById('sample')
  sample.value += e.innerText
}