Major_Version_Number.Minor_Version_Number[.Revision_Number[.Build_Number]]
 
主版本号   .子版本号    [.修正版本号  [.编译版本号 ]]

/**
 * 版本比较 VersionCompare
 * @param {String} currVer 当前版本.
 * @param {String} promoteVer 比较版本.
 * @return {Boolean} false 当前版本小于比较版本返回 true.
 *
 * 使用
 * VersionCompare("6.3","5.2.5"); // false.
 * VersionCompare("6.1", "6.1"); // false.
 * VersionCompare("6.1.5", "6.2"); // true.
 */
var VersionCompare = function (currVer, promoteVer) {
 currVer = currVer || "0.0.0";
 promoteVer = promoteVer || "0.0.0";
 if (currVer == promoteVer) return false;
 var currVerArr = currVer.split(".");
 var promoteVerArr = promoteVer.split(".");
 var len = Math.max(currVerArr.length, promoteVerArr.length);
 for (var i = 0; i < len; i++) {
  var proVal = ~~promoteVerArr[i],
   curVal = ~~currVerArr[i];
  if (proVal < curVal) {
   return false;
  } else if (proVal > curVal) {
   return true;
  }
 }
 return false;
};

VersionCompare("6.3","5.2.5"); // false.
VersionCompare("6.1", "6.1"); // false.
VersionCompare("6.1.5", "6.2"); // true.

var wechatInfo = navigator.userAgent.match(/MicroMessenger\/([\d\.]+)/i);
var currVer = wechatInfo[1];
if (VersionCompare(currVer, "6.2.5")) {
 //你的业务逻辑
}