TypeScript Modules - exporting and importing Re-export
Example
Typescript allow to re-export declarations.
//Operator.ts
interface Operator {
eval(a: number, b: number): number;
}
export default Operator;
//Add.ts
import Operator from "./Operator";
export class Add implements Operator {
eval(a: number, b: number): number {
return a + b;
}
}
//Mul.ts
import Operator from "./Operator";
export class Mul implements Operator {
eval(a: number, b: number): number {
return a * b;
}
}
You can bundle all operations in single library
//Operators.ts
import {Add} from "./Add";
import {Mul} from "./Mul";
export {Add, Mul};
Named declarations can be re-exported using shorter syntax
//NamedOperators.ts
export {Add} from "./Add";
export {Mul} from "./Mul";
Default exports can also be exported, but no short syntax is available. Remember, only one default export per module is possible.
//Calculator.ts
export {Add} from "./Add";
export {Mul} from "./Mul";
import Operator from "./Operator";
export default Operator;
Possible is re-export of bundled import
//RepackedCalculator.ts
export * from "./Operators";
When re-exporting bundle, declarations may be overridden when declared explicitly.
//FixedCalculator.ts
export * from "./Calculator"
import Operator from "./Calculator";
export class Add implements Operator {
eval(a: number, b: number): number {
return 42;
}
}
Usage example
//run.ts
import {Add, Mul} from "./FixedCalculator";
const add = new Add();
const mul = new Mul();
console.log(add.eval(1, 1)); // 42
console.log(mul.eval(3, 4)); // 12
