JS选择指定的文字

JS选择指定的文字，例如微博的话题. 

 function myField() {  var marker = "#";  var v = "在这里输入你想要说的话题";  var s1 =  marker + v + marker;  var myField = T$('wordstextarea');  var s2 = myField.value;  myField.focus();  if (window.getSelection)  {       var pos1 = s2.indexOf(s1);     if (pos1 == -1)  {     myField.value += s1;     pos1 = s2.length + 1;     }      else  {      pos1 += 1;     }  myField.selectionStart = pos1;  myField.selectionEnd = pos1 + s1.length - 2;  }   else   {  var  range=myField.createTextRange();    if (!range.findText(s1)){     myField.value += s1;     range.findText(s1);  }     range.findText(v);  range.select();   }}