you use const content = document.createElement ('div');

    content.contentEditable = true;
    // markdown
    let timer;
    content.addEventListener('input', (event) => {
        clearTimeout(timer);

        timer = setTimeout(() => {
            // html 
            console.log(String.fromCharCode(event.target.innerHTML));
        }, 500);
        event.preventDefault();
    }, false);

there is really no introduction to this thing on the Internet, so find out everything in the range and look for it manually. Portal-go to JSRUN to see the effect , Portal-check out W3 specification

you can also consider putting characters into canvas and then selecting all circles