Javascript HTML dynamically adds and removes text fields

Question

I am trying to dynamically add and remove text fields using javascript and HTML. I can add and remove it, but sometimes the delete button does not work. when I check the item, it says that there is no onclick value for the delete button. I do not understand why, when I set onclick in the add function.

Here is my code:

<div  id="reqs">
<h3 align = "center"> Requirements </h3>
<script>
    var reqs_id = 0;
    function removeElement(elementId,elementId2) {
        // Removes an element from the document
        var element2 = document.getElementById(elementId2);
        var element = document.getElementById(elementId);
        element2.parentNode.removeChild(element2);
        element.parentNode.removeChild(element);

    }   
    function add() {
        reqs_id++;// increment reqs_id to get a unique ID for the new element

        //create textbox
        var input = document.createElement('input');
        input.type = "text";
        input.setAttribute("class","w3-input w3-border");
        input.setAttribute('id','reqs'+reqs_id);
        var reqs = document.getElementById("reqs");
        //create remove button
        var remove = document.createElement('button');
        remove.setAttribute('id','reqsr'+reqs_id);
        remove.onclick = function() {removeElement('reqs'+reqs_id,'reqsr'+reqs_id);return false;};
        remove.setAttribute("type","button");
        remove.innerHTML = "Remove";
        //append elements
        reqs.appendChild(input);
        reqs.appendChild(remove);
    }

</script>
<button type="button" value="Add" onclick="javascript:add();"> Add</button> 

Answer 1

This will work:

<div id="reqs">
  <h3 align="center"> Requirements </h3>
</div>
<script>
  var reqs_id = 0;

  function removeElement(ev) {
    var button = ev.target;
    var field = button.previousSibling;
    var div = button.parentElement;
    div.removeChild(button);
    div.removeChild(field);
  }

  function add() {
    reqs_id++; // increment reqs_id to get a unique ID for the new element

    //create textbox
    var input = document.createElement('input');
    input.type = "text";
    input.setAttribute("class", "w3-input w3-border");
    input.setAttribute('id', 'reqs' + reqs_id);
    input.setAttribute('value', reqs_id);
    var reqs = document.getElementById("reqs");
    //create remove button
    var remove = document.createElement('button');
    remove.setAttribute('id', 'reqsr' + reqs_id);
    remove.onclick = function(e) {
      removeElement(e)
    };
    remove.setAttribute("type", "button");
    remove.innerHTML = "Remove" + reqs_id;
    //append elements
    reqs.appendChild(input);
    reqs.appendChild(remove);
  }

</script>
<button type="button" value="Add" onclick="javascript:add();"> Add</button>

Answer 2

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. JSFiddle.

HTML

<div id="reqs">
   <h3>Requirements</h3>
   <button type="button" value="Add" onclick="javascript:add();">Add</button>
   <br>
</div>

Javascript

function removeElement(e) {
    let button = e.target;
    let field = button.previousSibling;
    let div = button.parentElement;
    let br = button.nextSibling;
    div.removeChild(button);
    div.removeChild(field);
    div.removeChild(br);

    let allElements = document.getElementById("reqs");
    let inputs = allElements.getElementsByTagName("input");
    for(i=0;i<inputs.length;i++){
        inputs[i].setAttribute('id', 'reqs' + (i+1));
        inputs[i].setAttribute('value', (i+1));
        inputs[i].nextSibling.setAttribute('id', 'reqsr' + (i+1));
    }
}

function add() {
    let allElements = document.getElementById("reqs");
    let reqs_id = allElements.getElementsByTagName("input").length;
    reqs_id++;

    //create textbox
    let input = document.createElement('input');
    input.type = "text";
    input.setAttribute("class", "w3-input w3-border");
    input.setAttribute('id', 'reqs' + reqs_id);
    input.setAttribute('value', reqs_id);
    let reqs = document.getElementById("reqs");

    //create remove button
    let remove = document.createElement('button');
    remove.setAttribute('id', 'reqsr' + reqs_id);
    remove.onclick = function(e) {
        removeElement(e);
    };
    remove.setAttribute("type", "button");
    remove.innerHTML = "Remove";

    //append elements
    reqs.appendChild(input);
    reqs.appendChild(remove);
    let br = document.createElement("br");
    reqs.appendChild(br);
}