获取input文本框中高亮显示的值

<input value="dsafsdafweqrqwerwqer">
<button onclick="alert(document.selection.createRange().text)">ssss</button>



if(document.all){
var content = document.selection.createRange();
}else{
var content = window.getSelection();
content.text = content.toString();
}
var str = content.text;//选择的内容