es6 features in javascript

                                    // app.js
import ln, {pi, e} from "lib/mathplusplus";
alert("2π = " + ln(e)*pi*2);

                                    // lib/mathplusplus.js
export * from "lib/math";
export var e = 2.71828182846;
export default function(x) {
    return Math.log(x);
}

                                    // lib/math.js
export function sum(x, y) {
  return x + y;
}
export var pi = 3.141593;

                                    // otherApp.js
import {sum, pi} from "lib/math";
alert("2π = " + sum(pi, pi));

                                    // app.js
import * as math from "lib/math";
alert("2π = " + math.sum(math.pi, math.pi));