JSFiddle - React, Tailwind, and code Playground

HTML

<span id="editableContent" onclick="getCaret(this);" contenteditable=true>Hello, world<br> Good bye, World</span>

JavaScript

function getCaret(element) {
    var caretOffset = 0;
    if (typeof window.getSelection != "undefined") {
        var range = window.getSelection().getRangeAt(0);
        var preCaretRange = range.cloneRange();
        preCaretRange.selectNodeContents(element);
        preCaretRange.setEnd(range.endContainer, range.endOffset);
        caretOffset = preCaretRange.toString().length;
    } else if (typeof document.selection != "undefined" && document.selection.type != "Control") {
        var textRange = document.selection.createRange();
        var preCaretTextRange = document.body.createTextRange();
        preCaretTextRange.moveToElementText(element);
        preCaretTextRange.setEndPoint("EndToEnd", textRange);
        caretOffset = preCaretTextRange.text.length;
    }
    var elCont=element.innerHTML;
    
    var truncCont=elCont.substr(0,caretOffset);
    
    alert(truncCont);
}