选中/复制文字

获取手动选择的文字：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
    <textarea id="content" cols="30" rows="10">my name is yangkang!</textarea>
    <button id="btn">获取选中的文字</button>
    <div id="show"></div>
    <script>
    function selectText(id) {
        var oBox = document.getElementById(id);
        if(window.getSelection){
            if(oBox.selectionStart != undefined && oBox.selectionEnd != undefined){
                return oBox.value.substring(oBox.selectionStart,oBox.selectionEnd);
            }
            else{
                return "";
            }
        }
        else{
            return document.selection.createRange().text;
        }
    }
    document.getElementById(\'btn\').onclick = function () {
        document.getElementById(\'show\').innerHTML = selectText(\'content\');
    }
    </script>
</body>
</html>

自动选中文字：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
    <div id="myTxt">my name is yangk!</div>
    <script>
    function selectText(element) {
        var text = document.getElementById(element);
        if(document.body.createTextRange){
            var range = document.body.createTextRange();
            range.moveToElementText(text);
            range.select();
        }
        else if(window.getSelection){
            var selection = window.getSelection();
            var range = document.createRange();
            range.selectNodeContents(text);
            selection.removeAllRanges();
            selection.addRange(range);
            /*if(selection.setBaseAndExtent){
                selection.setBaseAndExtent(text, 0, text, 1);
            }*/
        }
        else{
            alert("none");
        }
    }
    selectText("myTxt");
    </script>
</body>
</html>

zclip插件（服务器环境下使用）：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <script src="jquery-1.11.1.js"></script>
    <script src="jquery.zclip.min.js"></script>
    <script>
    $(function(){ 
        $(\'#copyBtn\').zclip({ 
            path: \'ZeroClipboard.swf\', 
            copy: function(){//复制内容
                return $(\'#myTxt\').val();
                //return $(\'#myTxt\').text();//如果是div等非能输入元素
            }, 
            afterCopy: function(){//复制成功
                $("<span id=\'msg\'/>").insertAfter($(\'#copyBtn\')).text(\'复制成功\'); 
            } 
        }); 
    }); 
    </script>
</head>
<body>
    <textarea id="myTxt">请输入内容</textarea><br/> 
    <a href="javascript:;" id="copyBtn">复制内容</a>
</body>
</html>

execCommand

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
    <p>点击复制后在右边textarea CTRL+V看一下</p>
    <!-- 输入框 -->
    <input type="text" id="inputText" value="测试文本"/>
    <!-- 按钮 -->
    <input type="button" id="btn" value="复制"/>

    <textarea rows="4"></textarea>
    <script type="text/javascript">
        var btn = document.getElementById(\'btn\');
        btn.addEventListener(\'click\', function(){
            var inputText = document.getElementById(\'inputText\');

            // currentFocus 是复制按钮
            var currentFocus = document.activeElement;

            // 全选
            inputText.focus();
            inputText.setSelectionRange(0, inputText.value.length);

            // 复制
            document.execCommand(\'copy\', true);

            // 把光标从 inputText 中移出
            currentFocus.focus();
        });
    </script>
</body>
</html>