http://www.cnblogs.com/rainman/archive/2011/02/27/1966482.html
if(obj.createTextRange){//IE浏览器
var range = obj.createTextRange();
range.moveEnd("character",结束序号);
range.moveStart("character", 起始序号);
range.select();
}else{//非IE浏览器
obj.setSelectionRange(起始序号, 结束序号);
obj.focus();
}
selection createTextRange setSelectionRange
原文:http://www.cnblogs.com/znsongshu/p/6079388.html