在arcGIS api for js中（4.x），如何限制map的缩放级别？

var initialViewParams = { //MapView

      map: this.map,

      container: this.options.container,

      zoom: this.options.zoom, //当前缩放值

      center: this.options.center, //中心点位,

      highlightOptions: {

        fillOpacity: 0,

        color: [255, 0, 0, 0.8],

        haloOpacity: 0.8

      },

      constraints: { //设置约束条件

        minZoom: 9,

        maxZoom: 18

      }

    };