select change

html

<select name="cid" id="cid" class="form-control">
    <option value="">全部</option>
    {{range .category}}
    <option value="{{.id}}">{{.title}}</option>
    {{end}}
</select>

js

$("#cid").change(function () {
    location.href = location.pathname + '?' +
        new URLSearchParams(new FormData($("#searchForm")[0])).toString()
})