去除<!-- [if gte mso 9]><

var reg = /<!--\s+\[if\s+gte\s+mso\s+\d+\]>(?:(?!<!\[endif\]-->)[\s\S])*<!\[endif\]-->;
var str = '<!--[if gte mso 9]><xml>\r\n <o:OfficeDocumentSettings>\r\n  <o:RelyOnVML/>\r\n  <o:AllowPNG/>\r\n </o:OfficeDocumentSettings>\r\n</xml><![endif]--><span>一</span>\r\n<!--[if gte mso 9]><xml>\r\n <o:OfficeDocumentSettings>\r\n  <o:RelyOnVML/>\r\n  <o:AllowPNG/>\r\n </o:OfficeDocumentSettings>\r\n</xml><![endif]--><span>二</span>……';
str.replace(reg, "");