Write a breakpoints class in responsive web design with javascript

If you have to design a responsive design website(RWD), there is a easy class to judge with the various kinds of devices.

let breakPoints = {
        points :{ 
          phone: 320,
          tablet: 768,
          desktop: 1024,
        },
        
        isM: function () {
          if (window.innerWidth < this.points.tablet) {
            console.log("isMobile", window.innerWidth < this.points.tablet);
            return window.innerWidth < this.points.tablet;
          } else if ( window.innerWidth > this.points.phone && window.innerWidth < this.points.desktop) {
            console.log("isTable");
          } else if (window.innerWidth > this.points.desktop) {
            console.log("isDesktop");
            }
        },
        
        isT:  function () {
          if (window.innerWidth < this.points.tablet) {
            console.log("isMobile", window.innerWidth < this.points.tablet);
          } else if ( window.innerWidth > this.points.phone && window.innerWidth < this.points.desktop) {
            console.log("isTable");
            return (window.innerWidth > this.points.phone && window.innerWidth < this.points.desktop);
          } else if (window.innerWidth > this.points.desktop) {
            console.log("isDesktop");
            }
        },
        
        isD:function () {
          if (window.innerWidth < this.points.tablet) {
            console.log("isMobile", window.innerWidth < this.points.tablet);
          } else if ( window.innerWidth > this.points.phone && window.innerWidth < this.points.desktop) {
            console.log("isTable");
          } else if (window.innerWidth > this.points.desktop) {
            console.log("isDesktop");
            return (window.innerWidth > this.points.desktop);
            }
        }
    }