在光标处插入结点或字符串

function insertNodeAtCursor(node) {
    var range, html;
    if (window.getSelection && window.getSelection().getRangeAt) {
        range = window.getSelection().getRangeAt(0);
        range.insertNode(node);
    } else if (document.selection && document.selection.createRange) {
        range = document.selection.createRange();
        html = (node.nodeType == 3) ? node.data : node.outerHTML;
        range.pasteHTML(html);
    }
}

function insertHtmlAtCursor(html) {
    var range, node;
    if (window.getSelection && window.getSelection().getRangeAt) {
        range = window.getSelection().getRangeAt(0);
        node = range.createContextualFragment(html);
        range.insertNode(node);
    } else if (document.selection && document.selection.createRange) {
        document.selection.createRange().pasteHTML(html);
    }
}