transpile

transpile.test.ts

import transpile, { Writer } from './transpile';

describe('transpile', () => {

    describe('given a reader that always reads "foobarbaz"', () => {

        const reader = { read: () => 'foobarbaz' };

        describe('given a default writer', () => {

            const writer = new Writer();

            it('sequentially applies 2 mods and returns expected result as a string', () => {
                const result = transpile(
                    reader,
                    [
                        x => x.replace('foo', 'qux'),
                        x => x.replace('xbar', 'thud'),
                    ],
                    writer,
                );
                expect(result).toEqual('quthudbaz');
            });
        });

        describe('given a writer that is configured to write JSON', () => {

            const writer = new Writer('json');

            it('sequentially applies 2 mods and returns expected result as JSON', () => {
                const result = transpile(
                    reader,
                    [
                        x => x.replace('foo', 'qux'),
                        x => x.replace('xbar', 'thud'),
                    ],
                    writer,
                );
                expect(JSON.parse(result)).toEqual('quthudbaz');
            });
        });
    });
});

transpile.ts

export interface Reader {
    read(): string;
}

export class Writer {
    constructor(private format?: 'json' | string) {}
    public write(value: string) {
        return this.format === 'json' ? JSON.stringify(value) : value;
    }
}

export type Mod = (value: string) => string;

export default function transpile(
    reader: Reader,
    mods: Mod[],
    writer: Writer,
) {
    let text = reader.read();
    mods.forEach(mod => {
        text = mod(text);
    });
    return writer.write(text);
}