不多說

範例如下:https://codepen.io/rstrahl/pen/mpXEEE

需要include jquery跟https://rawgit.com/RickStrahl/jquery-resizable/master/src/jquery-resizable.js

CSS 部分
html,
 body {
   height: 100%;
   font-family: 'Trebuchet MS', 'Lucida Sans Unicode', 'Lucida Grande', 'Lucida Sans', Arial, sans-serif;
   padding: 0;
   margin: 0;
   overflow: auto;
 }
 .page-container {
   margin: 20px;
 }
 /* horizontal panel*/
 .panel-container {
   display: flex;
   flex-direction: row;
   border: 1px solid silver;
   overflow: hidden;  
   /* avoid browser level touch actions */
   xtouch-action: none;
 }
 .panel-left {
   flex: 0 0 auto;
   /* only manually resize */
   padding: 10px;
   width: 300px;
   min-height: 200px;
   min-width: 150px;
   white-space: nowrap;
   background: #838383;
   color: white;
 }
 .splitter {
   flex: 0 0 auto;
   width: 18px;  
   background: url(https://raw.githubusercontent.com/RickStrahl/jquery-resizable/master/assets/vsizegrip.png) center center no-repeat #535353;
   min-height: 200px;
   cursor: col-resize;  
 }
 .panel-right {
   flex: 1 1 auto;
   /* resizable */
   padding: 10px;
   width: 100%;
   min-height: 200px;  
   background: #eee;
 }
 /* vertical panel */
 .panel-container-vertical {
   display: flex;
   flex-direction: column;
   height: 500px;
   border: 1px solid silver;
   overflow: hidden;
 }
 .panel-top {
   flex: 0 0 auto;
   /* only manually resize */
   padding: 10px;
   height: 150px;
   width: 100%;
   white-space: nowrap;
   background: #838383;
   color: white;
 }
 .splitter-horizontal {
   flex: 0 0 auto;
   height: 18px;
   background: url(https://raw.githubusercontent.com/RickStrahl/jquery-resizable/master/assets/hsizegrip.png) center center no-repeat #535353;
   cursor: row-resize;
 }
 .panel-bottom {
   flex: 1 1 auto;
   /* resizable */
   padding: 10px;
   min-height: 200px;
   background: #eee;
 }
 label {
   font-size: 1.2em;
   display: block;
   font-weight: bold;
   margin: 30px 0 10px;
 }
 pre {
   margin: 20px;
   padding: 10px;
   background: #eee;
   border: 1px solid silver;
   border-radius: 4px;
   overflow: auto;
 }

JS部分
$(".panel-left").resizable({
    handleSelector: ".splitter",
    resizeHeight: false   
  });
 $(".panel-top").resizable({
    handleSelector: ".splitter-horizontal",
    resizeWidth: false
 });