JSFiddle - React, Tailwind, and code Playground

HTML

<div id="div">
    Here is some text
    <br><br>
    <b>More text</b>
</div>

JavaScript

function getTextNodeHeight(textNode) {
    var height = 0;
    if (document.createRange) {
        var range = document.createRange();
        range.selectNodeContents(textNode);
        if (range.getBoundingClientRect) {
            var rect = range.getBoundingClientRect();
            if (rect) {
                height = rect.bottom - rect.top;
            }
        }
    }
    return height;
}

var textNode = document.getElementById("div").firstChild;
alert(getTextNodeHeight(textNode));