对象本田CRV

<script>
    window.onload = function (ev) {
        var vcar = new Car("本田", "CRV", 45, 2);
        vcar.startup();
        vcar.Startengine();
        vcar.changeSpeed();
        vcar.swerve();
        vcar.stop();
        vcar.Turnofftheengine();
    }

    function Car(make, model, currentSpeed, displacement) {
        var currentSpeed = currentSpeed;
        this.startup = function () {
            document.write("启动:0")
        }
        this.Startengine= function () {
            var speed = currentSpeed;
            document.write("<br>"+"启动引擎:"+speed)
        }
        this.changeSpeed = function () {
            var speed = currentSpeed+20;
            document.write("<br>"+"加速:"+speed)
        }
        this.swerve = function () {
            var speed = currentSpeed-20;
            document.write("<br>"+"转向:"+speed)
        }
        this.stop = function () {
            var speed = 0;
            document.write("<br>"+"刹车:"+speed)
        }
        this.Turnofftheengine = function () {
            var speed = currentSpeed-25;
            document.write("<br>"+"关引擎:"+speed)
        }
    }
</script>