intercept form submit with jQuery

You can’t return out of a callback to an asynchronous method(such as ajax). Instead, prevent the submit all together, then submit it when you are ready.

$("#methodForm").submit(function(e){
    e.preventDefault();
    var form = this;
    checkIndex('upload/segments.gen').done(function() {
        form.submit(); // submit bypassing the jQuery bound event
    }).fail(function () {
        alert("No index present!");
    });
});