$(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>

    $(document).ready(function() {

        var $cr = $("#cr");

        $cr.click(function() {

            if ($cr.is(":checked")) {

                alert("thank you support,continue")

            }

        })

    })