jQuery.extend({
    /**
     * 清除当前选择内容
     */
    unselectContents: function(){
        if(window.getSelection)
            window.getSelection().removeAllRanges();
        else if(document.selection)
            document.selection.empty();
    }
});
jQuery.fn.extend({
    /**
     * 选中内容
     */
    selectContents: function(){
        $(this).each(function(i){
            var node = this;
            var selection, range, doc, win;
            if ((doc = node.ownerDocument) &&
                (win = doc.defaultView) &&
                typeof win.getSelection != 'undefined' &&
                typeof doc.createRange != 'undefined' &&
                (selection = window.getSelection()) &&
                typeof selection.removeAllRanges != 'undefined')
            {
                range = doc.createRange();
                range.selectNode(node);
                if(i == 0){
                    selection.removeAllRanges();
                }
                selection.addRange(range);
            }
            else if (document.body &&
                     typeof document.body.createTextRange != 'undefined' &&
                     (range = document.body.createTextRange()))
            {
                range.moveToElementText(node);
                range.select();
            }
        });
    },
    /**
     * 初始化对象以支持光标处插入内容
     */
    setCaret: function(){
        if(!$.browser.msie) return;
        var initSetCaret = function(){
            var textObj = $(this).get(0);
            textObj.caretPos = document.selection.createRange().duplicate();
        };
        $(this)
        .click(initSetCaret)
        .select(initSetCaret)
        .keyup(initSetCaret);
    },
    /**
     * 在当前对象光标处插入指定的内容
     */
    insertAtCaret: function(textFeildValue){
       var textObj = $(this).get(0);
       if(document.all && textObj.createTextRange && textObj.caretPos){
           var caretPos=textObj.caretPos;
           caretPos.text = caretPos.text.charAt(caretPos.text.length-1) == '' ?
                               textFeildValue+'' : textFeildValue;
       }
       else if(textObj.setSelectionRange){
           var rangeStart=textObj.selectionStart;
           var rangeEnd=textObj.selectionEnd;
           var tempStr1=textObj.value.substring(0,rangeStart);
           var tempStr2=textObj.value.substring(rangeEnd);
           textObj.value=tempStr1+textFeildValue+tempStr2;
           textObj.focus();
           var len=textFeildValue.length;
           textObj.setSelectionRange(rangeStart+len,rangeStart+len);
           textObj.blur();
       }
       else {
           textObj.value+=textFeildValue;
       }
    }
});