Wrap first letter of Sentence in tag (span) with class

js

$(function(){
    var a = new String;
    a = $('.section-heading').html();
    var b = a.indexOf(' '); 
    if (b == -1) {
        b = a.length;
    }
    $('.section-heading').html('<span>'+a.substring(0, 1)+'</span>'+a.substring(b, 1)+a.substring(b, a.length));
});