javascrip t截取字符串

<script type="text/javascript">

$(function(){

$("img.hover").hover(

function(){

var strName=$(this).attr('src');

var index=strName.lastIndexOf('.');

var strLeft=strName.substring(0,index);

var strRight=strName.substring(index,strName.length); //varstrName=$(this).attr('src').replace("b.gif",".gif");//使用这个会出问题

$(this).attr("src",strLeft+'b'+strRight);

},

function(){

var strName=$(this).attr('src');

var index=strName.lastIndexOf('.');

var strLeft=strName.substring(0,index-('b').length);

var strRight=strName.substring(index,strName.length);

$(this).attr("src",strLeft+strRight);

});

});

</script>