var filename = "./src/pages/scene/register/register.ejs";
    //ext = /[^.]+$/.exec(filename);
    ext = filename.split('.').pop();
    console.log(ext);

// 不用正則的方案
const extname = (filename) => {
  if(typeof filename === 'string' && [-1,0].indexOf(filename.lastIndexOf('.')) === -1){
   return filename.slice(filename.lastIndexOf('.'));
  }else{
    return '';
  }
}
var result = extname('./src/pages/scene/register/register.js');
console.log(result); // '.js'
var result2 = extname('./src/pages/scene/register/register.ejs');
console.log(result2); // '.ejs'

var regex=/\.[^.]+$/;
var str="./src/pages/scene/register/register.js";
str.match(regex)[0];