ECMAScript Module Default and Named Export

The module mechanism in ECMAScript is used to split code into multiple files and control the export and import of modules, facilitating the organization and management of large projects.
ECMAScript modules utilize standardized import and export syntax to export one or more values from a module and then import and use these values in another module. For example:

// module1.js
export const foo = 1;
export function bar() {
  console.log('bar');
}
// module2.js
import { foo, bar } from './module1.js';
console.log(foo);
bar();

In the above example, module1.js exports foo and bar using the export keyword, while module2.js imports and uses these values using the import syntax.
In addition to importing and exporting single values, the ECMAScript module mechanism also supports default exports and namespace exports. A default export can be exported using the export default syntax for a single default value, while a namespace export can re-export all exports from a module as a namespace using the export * syntax. For example:

// module1.js
const foo = 1;
function bar() {
  console.log('bar');
}
export default foo;
export { bar };
// module2.js
import myFoo, * as myModule1 from './module1.js';
console.log(myFoo);
myModule1.bar();

In the above example, module1.js exports the default value foo using the export default keyword and also exports the bar function. In module2.js, the default value foo is imported using the import myFoo syntax, while all exports from module1.js are re-exported as a myModule1 namespace using the import * as myModule1 syntax.
Overall, the module mechanism in ECMAScript provides a way to organize and manage code, helping developers better organize and maintain large projects.

Default Export and Namespace

In ECMAScript, export and import syntax are used to export and import values from modules. In addition to regular imports and exports, there are two special types of imports and exports: default exports and namespace exports.
A default export refers to a module exporting only one default value, which can be any type of value, including functions, objects, primitive data types, etc. A default export can be exported using the export default syntax. For example:

// module1.js
export default function() {
  console.log('default function');
}
// module2.js
import myFunction from './module1.js';
myFunction(); // Outputs "default function"

In the above example, module1.js exports a default function using export default, while module2.js imports the default function using the import myFunction from './module1.js' syntax and assigns it an alias myFunction.
A namespace export refers to re-exporting all exports from a module as a single namespace. This namespace can contain all exports from the module or choose to export only a subset of them. A namespace export can be exported using the export * as syntax. For example:

// module1.js
export const foo = 1;
export function bar() {
  console.log('bar');
}
// module2.js
export * as myModule1 from './module1.js';

In the above example, module2.js re-exports all exports from module1.js as a single myModule1 namespace using the export * as myModule1 from './module1.js' syntax. Exports from module1.js can then be accessed via myModule1.foo and myModule1.bar().
It is important to note that if a module uses both default exports and namespace exports, the value of the default export will not be included in the namespace.