add html elements clicking a button

 <form action="" method="post" id="form">

    <div class="textfields-container">

        <div class="textfield-container"></div>

    </div>

    <input type="button" name="addTextfield" id="addTextfield" value="Add Textfield"/>

    <input type="submit" value="Submit"/>

</form>

<script>

    document.getElementById("addTextfield").addEventListener("click", function(){

        var textfield = document.createElement("input");

        textfield.type = "text";

        textfield.name = "textfield[]";

        var textfieldContainer = document.querySelector(".textfields-container");

        textfieldContainer.appendChild(textfield);

    });

</script>