xssbook/public/js/main.js

var range;

function add(html, id) {
    const old = document.getElementById(id)
    if (old !== null) {
        old.remove()
    }
    if (range === undefined) {
        var range = document.createRange()
        range.setStart(document.body, 0)
    }
    document.body.appendChild(
        range.createContextualFragment(html)
    )
}