FAQ: diffence of import and require

[malleus35]

Hello, I want to use seneca with Typescript.
So, I import seneca node package to use import statement.
I run tutorial code to have little change. Like this.

import Seneca from "seneca";
const seneca = Seneca();

seneca.add({ role: "math", cmd: "sum" }, function (
  msg: any,
  respond: Function
) {
  var sum = msg.left + msg.right;
  respond(null, { answer: sum });
});

seneca.add({ role: "math", cmd: "product" }, function (
  msg: any,
  respond: Function
) {
  var product = msg.left * msg.right;
  respond(null, { answer: product });
});

seneca
  .act({ role: "math", cmd: "sum", left: 1, right: 2 }, console.log)
  .act({ role: "math", cmd: "product", left: 3, right: 4 }, console.log); // This line has Error
/*
*  Property 'act' does not exist on type 'void'.ts(2339)
*/

Could you tell me how can i use ES6 module system?
If this problem can't solve without CommonJS module system, then i use require statement.
Thanks