export

// Exporting declarations
export let name1, name2/*, … */; // also var
export const name1 = 1, name2 = 2/*, … */; // also var, let
export function functionName() { /* … */ }
export class ClassName { /* … */ }
export function* generatorFunctionName() { /* … */ }
export const { name1, name2: bar } = o;
export const [ name1, name2 ] = array;

// Export list
export { name1, /* …, */ nameN };
export { variable1 as name1, variable2 as name2, /* …, */ nameN };
export { variable1 as "string name" };
export { name1 as default /*, … */ };

// Default exports
export default expression;
export default function functionName() { /* … */ }
export default class ClassName { /* … */ }
export default function* generatorFunctionName() { /* … */ }
export default function () { /* … */ }
export default class { /* … */ }
export default function* () { /* … */ }

// Aggregating modules
export * from "module-name";
export * as name1 from "module-name";
export { name1, /* …, */ nameN } from "module-name";
export { import1 as name1, import2 as name2, /* …, */ nameN } from "module-name";
export { default, /* …, */ } from "module-name";
export { default as name1 } from "module-name";

// export features declared elsewhere
export { myFunction2, myVariable2 };

// export individual features (can export var, let,
// const, function, class)
export let myVariable = Math.sqrt(2);
export function myFunction() {
  // …
}

export using resource1 = getResource(); // SyntaxError

// Allowed by syntax but discouraged
using resource2 = getResource();
export { resource2 };

export { x };
const x = 1;
// This works, because `export` is only a declaration, but doesn't
// utilize the value of `x`.

// export feature declared elsewhere as default
export { myFunction as default };
// This is equivalent to:
export default myFunction;

// export individual features as default
export default function () { /* … */ }
export default class { /* … */ }

export default 1 + 1;

// Works because `foo` is a function declaration,
// not a function expression
foo();

export default function foo() {
  console.log("Hi");
}

// It's still technically a declaration, but it's allowed
// to be anonymous
export default function () {
  console.log("Hi");
}

// file test.js
const k = 12;
export default k;

// some other file
import m from "./test"; // note that we have the freedom to use import m instead of import k, because k was default export

console.log(m); // 12

export { myFunction as function1, myVariable as variable };

export { myFunction as "my-function" };

export { default as function1, function2 } from "bar.js";

import { default as function1, function2 } from "bar.js";

export { function1, function2 };

export { x } from "mod";
export { x as v } from "mod";
export * as ns from "mod";

// -- mod1.js --
export const a = 1;

// -- mod2.js --
export const a = 3;

// -- barrel.js --
export * from "./mod1.js";
export * from "./mod2.js";

// -- main.js --
import * as ns from "./barrel.js";

console.log(ns.a); // undefined

import { a } from "./barrel.js";
// SyntaxError: The requested module './barrel.js' contains conflicting star exports for name 'a'

export DefaultExport from "bar.js"; // Invalid

export { default as DefaultExport } from "bar.js";

export { default, function2 } from "bar.js";

export { default } from "./data.json" with { type: "json" };

// module "my-module.js"
function cube(x) {
  return x * x * x;
}

const foo = Math.PI + Math.SQRT2;

const graph = {
  options: {
    color: "white",
    thickness: "2px",
  },
  draw() {
    console.log("From graph draw function");
  },
};

export { cube, foo, graph };

import { cube, foo, graph } from "./my-module.js";

graph.options = {
  color: "blue",
  thickness: "3px",
};

graph.draw(); // Logs "From graph draw function"
console.log(cube(3)); // 27
console.log(foo); // 4.555806215962888

// module "cube.js"

export default function cube(x) {
  return x * x * x;
}

import cube from "./cube.js";

console.log(cube(3)); // 27

// In childModule1.js
function myFunction() {
  console.log("Hello!");
}
const myVariable = 1;
export { myFunction, myVariable };

// In childModule2.js
class MyClass {
  constructor(x) {
    this.x = x;
  }
}

export { MyClass };

// In parentModule.js
// Only aggregating the exports from childModule1 and childModule2
// to re-export them
export { myFunction, myVariable } from "childModule1.js";
export { MyClass } from "childModule2.js";

// In top-level module
// We can consume the exports from a single module since parentModule
// "collected"/"bundled" them in a single source
import { myFunction, myVariable, MyClass } from "parentModule.js";