尝试此代码段

(function() {
  window.onresize = displayWindowSize;
  window.onload = displayWindowSize;

  function displayWindowSize() {
    let myWidth = window.innerWidth;
    let myHeight = window.innerHeight;
    // your size calculation code here
    document.getElementById("screen").innerHTML = myWidth + "x" + myHeight;
  };


})();

<div id="screen"></div>