var filename = file.name;
var index1 = filename.lastIndexOf(".");
var index2 = filename.length;
var ext = filename.substring(index1 + 1, index2);//后缀名
var filename = file.name;
var index1 = filename.lastIndexOf(".");
var index2 = filename.length;
var ext = filename.substring(index1 + 1, index2);//后缀名