regular.html

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width,initial-scale=1,user-scalable=0">
  <meta name="renderer" content="webkit">
  <title>正则</title>
  <meta name="description" content="首页描述"/>
  <meta name="keywords" content="首页关键词"/>
  <meta name="author" content="Web Layout:amu"/>
  <meta name="format-detection" content="telephone=no,date=no,address=no,email=no,url=no"/>

</head>
<body>
  <h2></h2>
  
  <script>
    let reg ={
      integer:/^(([^0][0-9]+|0)$)|^(([1-9]+)$)/
    }
    console.log(reg.integer.test(10))

    function fiterStr(str1,str2){
      var l = str1.length > str2.length ? str2.length : str1.length, //取短的
        i = 0
      while(i < l){
        if(str1[i] !== str2[i])break
        i++
      }
      return str1.substr(0,i)
    }
    let beforeStr = '【低至2999元 享12期免息】华为旗下荣耀V30双模5G麒麟990旗舰芯片李现同款'
    let aftereStr = '【低至5999元 享6期免息】华为旗下荣耀V30双模5G麒麟990旗舰芯片全友同款'
    //fiterStr(beforeStr,aftereStr);
    console.log(fiterStr(beforeStr,aftereStr))
  </script>
</body>
</html>