Untitled

make keyword into link automatically, globally
var span = $('span');
    span.html(function(i,html){
        replaceTextWithHTMLLinks(html);
    }); // jQuery version 1.4.x


function replaceTextWithHTMLLinks(text) {
  var exp = /(apple)/ig;
    return text.replace(exp,"<a class='link' href='http://www.$1.com' target='_blank' >$1</a>");
}

<span>
An apple a day, makes 7 apples a week!
</span>

(function($) {
    $.fn.replacetext = function(target, replacement) {
         // Get all text nodes:
         var $textNodes = this
                 .find("*")
                 .andSelf()
                 .contents()
                 .filter(function() {
                     return this.nodeType === 3 &&
                         !$(this).parent("a").length;
                 });

         // Iterate through the text nodes, replacing the content
         // with the link:
         $textNodes.each(function(index, element) {
             var contents = $(element).text();
             contents = contents.replace(target, replacement);
             $(element).replaceWith(contents);
         });
    };
})(jQuery);

$("body").replacetext(/apple/gi, "<a href='http://www.$&.com'>$&</a>");