JSFiddle - React, Tailwind, and code Playground

HTML

<div style='height:auto; font-size:2em;'>
  <i class='fas fa-minus-circle minus-btn' data-step="-1">-1</i>
  <input type='text' name='kolvo' value='1'>
  <i class='fas fa-plus-circle plus-btn' data-step="1">1</i>
</div>

JavaScript

$('i').on('click', function(e) {
  const input = $(e.target).parent().find('input')
  input.val(+input.val() + +$(e.target).data('step'))
})