如何在节点中导出 JS 模块

Question

I'm trying to import a string.prototype.method in a test file.

MODULE FILE:

module.exports = String.prototype.camelCase = function camelCase() {
  let string = "";
  this.split(" ")
    .map((el, i) => {
      i == 0
        ? (string += el.replace(/^\w/, (c) => c.toLowerCase()))
        : (string += el.replace(/\w/, (c) => c.toUpperCase()));
    })
    .join("");
  return string;
};

TEST FILE:

const test = require("ava");
import { camelCase } from "./index.js";

test("test", (t) => {
  t.pass("hello world".camelCase(), "HelloWorld");
});

when I trun npm test that's what ava return:

> js-util-library@1.0.0 test
> ava


  ✖ No tests found in test.mjs

  ─

  Uncaught exception in test.mjs

  file:///home/xlrnz/Documenti/dev/js-util-library/test.mjs:2
  import { camelCase } from "./index.js";
           ^^^^^^^^^
  SyntaxError: Named export 'camelCase' not found. The requested module './index.js' is a CommonJS module, which may not support all module.exports as named exports.

I don't understand, maybe some problem with string.prototype methods on export?

Thanks to @vitaliykotov I've learned something that previously I don't know.

Everything beautiful but now when I try npm test with this file:

const test = require('ava')

that's the result:

> js-util-library@1.0.0 test
> ava test.js


  ✖ No tests found in test.js

  ─

  Uncaught exception in test.js

  ReferenceError: require is not defined

  › file://test.js:1:14

Answer 1

As said in the error your module(and all modules in Node by default) is CommonJS module. So to import something from it you should use require() function. Also it's possible to tell Node to treat modules as ECMAScript , but then all modules should be defined this way