function pasteHtmlAtCaret(html, selectPastedContent) {
//参数1为要插入的html 
//参数2为boolean 是否选中插入的html 默认为false

    var sel, range;

    if (window.getSelection) {

        // IE9 and non-IE

        sel = window.getSelection();

        if (sel.getRangeAt && sel.rangeCount) {

            range = sel.getRangeAt(0);

            range.deleteContents();

            // Range.createContextualFragment() would be useful here but is

            // only relatively recently standardized and is not supported in

            // some browsers (IE9, for one)

            var el = document.createElement("div");

            el.innerHTML = html;

            var frag = document.createDocumentFragment(), node, lastNode;

            while ( (node = el.firstChild) ) {

                lastNode = frag.appendChild(node);

            }

            var firstNode = frag.firstChild;

            range.insertNode(frag);

            // Preserve the selection

            if (lastNode) {

                range = range.cloneRange();

                range.setStartAfter(lastNode);

                if (selectPastedContent) {

                    range.setStartBefore(firstNode);

                } else {

                    range.collapse(true);

                }

                sel.removeAllRanges();

                sel.addRange(range);

            }

        }

    } else if ( (sel = document.selection) && sel.type != "Control") {

        // IE < 9

        var originalRange = sel.createRange();

        originalRange.collapse(true);

        sel.createRange().pasteHTML(html);

        if (selectPastedContent) {

            range = sel.createRange();

            range.setEndPoint("StartToStart", originalRange);

            range.select();

        }

    }

}