CODE EXAMPLE FOR JAVASCRIPT

js paste event

const target = document.querySelector('div.target');

target.addEventListener('paste', (event) => {
    let paste = (event.clipboardData || window.clipboardData).getData('text');
    paste = paste.toUpperCase();
 
    const selection = window.getSelection();
    if (!selection.rangeCount) return false;
    selection.deleteFromDocument();
    selection.getRangeAt(0).insertNode(document.createTextNode(paste));

    event.preventDefault();
});