JSFiddle - React, Tailwind, and code Playground

HTML

<div id="landing-page">
<a href="/catalog.php?N=3000027652">catalog link 1</a>

    <br/>
<a href="/catalog.php?N=3000000000">catalog link 2</a>

    <br/>
<a href="http://www.mydomain.com/catalog.php?N=3000023333">catalog with domain</a>

    <br/>
<a href="/upgrade/wishlist.php">upgrade link</a>

    <br/> <a href="http://www.pinterest.com">Pinterest</a>

</div>

JavaScript

var foo = [
    '/catalog.php',
    '/upgrade'];

$.each(foo, function (i, value) {
    $('#landing-page').find('a[href^="' + value + '"]').attr('href', function(i, value) {
        return 'http://www.mydomain.com' + value;
    });
});