You can remove the href attribute when the input element is focused. As long as there is no href attribute, you will be able to select text inside the input field (tested in safari, chrome and firefox).
<a href="http://www.google.de" id="link">
link
<input type="text" id="input">
</a>
(function () {
var link = document.getElementById('link');
var input = document.getElementById('input');
var saveHref = null;
input.addEventListener('focusin', function () {
savedHref = link.href;
link.removeAttribute('href');
});
input.addEventListener('focusout', function () {
link.href = savedHref;
savedHref = null;
});
})();
Working example: http://codepen.io/jjd/pen/JYwLVr