单击时调整div的大小

<div id="myDiv" style="width: 200px; height: 200px; background-color: #ccc;"></div>

var myDiv = document.getElementById("myDiv");
var isResizing = false;
var startX, startY;

myDiv.addEventListener("mousedown", function(e) {
  isResizing = true;
  startX = e.clientX;
  startY = e.clientY;
});

document.addEventListener("mousemove", function(e) {
  if (!isResizing) return;
  
  var width = e.clientX - startX;
  var height = e.clientY - startY;
  
  myDiv.style.width = width + "px";
  myDiv.style.height = height + "px";
});

document.addEventListener("mouseup", function() {
  isResizing = false;
});