chinax.jianzhanzj.com/e/data/js/addplface.js

function eaddplface(tag) {
        var myField;
        if (document.getElementById('saytext') && document.getElementById('saytext').type == 'textarea') {
                myField = document.getElementById('saytext');
        }
        else {
                return false;
        }
        if (document.selection) {
                myField.focus();
                sel = document.selection.createRange();
                sel.text = tag;
                myField.focus();
        }
        else if (myField.selectionStart || myField.selectionStart == '0') {
                var startPos = myField.selectionStart;
                var endPos = myField.selectionEnd;
                var cursorPos = endPos;
                myField.value = myField.value.substring(0, startPos)
                                          + tag
                                          + myField.value.substring(endPos, myField.value.length);
                cursorPos += tag.length;
                myField.focus();
                myField.selectionStart = cursorPos;
                myField.selectionEnd = cursorPos;
        }
        else {
                myField.value += tag;
                myField.focus();
        }
}