jquery checkbox

    $(document).ready(function() {
        var $cr = $("#cr");
        var cr = $cr[0];
        $cr.click(function() {
        alert("click")
            if (cr.checked) {
                alert("thank you support,continue")
            }
        })
    })

    <input type="checkbox" id="cr" />
    <label for="cr">我同意条款</label>

jquery

    $(document).ready(function() {
        var $cr = $("#cr");

        $cr.click(function() {

            if ($cr.is(":checked")) {
                alert("thank you support,continue")
            }
        })
    })