JSFiddle - React, Tailwind, and code Playground

HTML

<form id="theForm">
  <div class="formDiv">
    THING
    <div class="innerContainer">
      <input type="text" placeholder="Textbox"/>
      <button class="innerBtn">Add new input</button>
    </div>
  </div>
  <br>
  <button id="deadlyBtn">I append to body, breaking the above button</button>
</form>

CSS

input{
  display:block;
}

JavaScript

//.innerBtn is a class because there could be several copies generated

$("#theForm").on("click", ".formDiv .innerContainer .innerBtn", function(e){
	e.preventDefault()
  $(this).before($('<input type="text" placeholder="Textbox"/>'))
})
$("#deadlyBtn").click(function(e){
	e.preventDefault()
  $('body').append("Now try clicking [Add new Input]")
  //document.body.innerHTML += "Now try clicking [Add new Input]"
})