Edit in JSFiddle

$(document).ready(function(){
    var str = 'jQuery By Example';
    $('#spnBeforeSubstring').html(str);
    $('#spnAfterSubstring').html(str.substr(2,12));
});

<b>Actual String : </b> <span id='spnBeforeSubstring'> </span>
<br/><br/>
<b>After Substring :</b> <span id='spnAfterSubstring'> </span><br/><b><i>(called substr(2,12))</i></b>