Programatically trigger form validation with JQuery Validator don't work - jquery-validate

Question

According to the docs of jQuery Validator doing this should programatically trigger form validation.
var validator = $( "#myform" ).validate();
validator.form();
But in my code it does nothing, why? I have a submit button on my form that is working fine, but validator.form() doesn't work at all. I've updated the post with my HTML form as well as the javascript code.
This is my form
<form class="kt-form kt-form--label-right" id="frm_sok" action="ajax/artikkel.php?a=sok_artikler" method="post">
<div class="kt-portlet__body">
<div class="kt-blog-post">
<div class="form-group ">
<div class="col-12">
<input class="form-control" type="search" value="{{ sok }}" id="searchinput" name="searchinput">
</div>
</div>
<div class="row">
<div class="col-4">
<label>Ikke søk i :</label>
<div class="form-check">
<input class="form-check-input" type="checkbox" value="1" id="skjulnyheter" name="skjulnyheter">
<label class="form-check-label" for="skjulnyheter">Nyheter</label>
</div>
<div class="form-check">
<input class="form-check-input" type="checkbox" value="1" id="skjulforum" name="skjulforum">
<label class="form-check-label" for="skjulforum">Forum</label>
</div>
</div>
<div class="col-4">
<label for="sorter">Sorter:</label><br />
<select class="form-control" name="sorter" id="sorter">
<option value="a.opp_dato DESC">Nyeste</option>
<option value="score">Beste treff</option>
<option value="a.opp_dato ASC">Eldste</option>
</select>
</div>
</div>
</div>
</div>
<div class="kt-portlet__foot">
<div class="kt-form__actions">
<input type="submit" class="btn btn-primary sokknapp" value="Søk" />
</div>
</div>
</form>
Here is my Javascript:
$( window ).on( 'load', function()
{
var validator = $("#frm_sok").validate(
{
rules:
{
searchinput:
{
required: true
}
},
messages:
{
searchinput :
{
required : 'Du må neste søke etter noe. Noe som helst. Ett eller annet.'
}
},
invalidHandler: function(event, validator)
{
$('.error').css( "display", "inline-block !important");
},
submitHandler: function(form)
{
preload_kamp();
$(form).ajaxSubmit(
{
success: function(data)
{
$( "#sokcontent" ).html(data);
}
});
}
});
validator.form();
});