npm install --save step-pipe

import { Step, PipeContext } from '../out';

// simple
function step1() {
    return (context: PipeContext<string>) => {
        console.log('step start');
        context.next('I am step 1 result');
    };
}

// delay callback
function step2() {
    return (context: PipeContext<string>) => {
        console.log(context.content);
        setTimeout(() => {
            context.next('I am step 2 result');
        }, 300);
    };
}

// with options
function step3(options?: { result?: string }) {
    if (!options) {
        options = {}
    };
    if (!options.result) {
        options.result = '';
    }

    return (context: PipeContext<string>) => {
        console.log(context.content);
        setTimeout(() => {
            context.next(options.result);
        }, 300);
    };
}

// use async/await
function step4() {
    return async (context: PipeContext<string>) => {
        console.log(context.content);
        const date = await Promise.resolve(new Date());
        await context.next('I am step 4 result:' + date.toLocaleDateString());
    };
}

function step5() {
    return async (context: PipeContext<string>) => {
        console.log(context.content);

        const createPromises = () => {
            const promises: Promise<string>[] = [];
            for (let i = 0; i < 10; i++) {
                promises.push(new Promise((c , e) => {
                    setTimeout(() => {
                        c(i + '');
                    }, Math.random() * 5000);
                }));
            }
            return promises;
        }

        const promises1 = createPromises();

        // parallel execution
        const p = promises1.map(async promise => {
            const result = await promise; 
            await context.next('parallel step:' + result);
        });

        await Promise.all(p);

        const promises2 = createPromises();

        // serial execution
        for (let i = 0; i < promises2.length; i++) {
            const result = await promises2[i];
            await context.next('serial step:' + result);
        }
    };
}

function end() {
    return async (context: PipeContext<string>) => {
        console.log(context.content);
    }
}

const step = new Step();

step.pipe(step1())
    .pipe(step2())
    .pipe(step3({ result: 'I am step 3 result' }))
    .pipe(step4())
    .pipe(step5())
    .pipe(end());

step.catch(error => {
    console.log(error);
});

step.start();