How to append/prepend/create a text node with jQuery

The createTextNode approach is probably the best way to go. If you want to have a jQuery-ish syntax, you could make a plugin.

$.fn.appendText = function(text) {
    return this.each(function() {
        var textNode = document.createTextNode(text);
        $(this).append(textNode);
    });
};

$.text() accepts also a function as parameter. This function will receive an index and the current text. The return value of the function will be set as the new text.

.text( function )

function
Type: Function( Integer index, String text ) => String
A function returning the text content to set. Receives the index position of the element in the set and the old text value as arguments.

$("li").text(function(idx, txt) {
   return txt + " <item>";
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<ul>
    <li>1</li>
    <li>2</li>
    <li>3</li>
</ul>