准备练习rxjs的环境

创建一个文件夹，例如rxjs-test

mkdir rxjs-test
cd rxjs-test

创建一个node工程

npm init

加入rxjs

yarn add rxjs
或者
npm install rxjs

创建index.js文件

touch index.js

const { interval, Observable } = require("rxjs");
const { filter, map, take, toArray } = require("rxjs/operators");

/**
 * 取每第N个值的操作符
 */
/* tslint:disable */
const takeEveryNth = (n) => (source) =>
    new Observable(observer => {
        let count = 0;
        return source.subscribe({
            next(x) {
                if (count++ % n === 0) { observer.next(x); }
            },
            error(err) { observer.error(err); },
            complete() { observer.complete(); }
        });
    });

/**
 * 还可以使用现有的操作符
 */
const takeEveryNthSimple = (n) => (source) =>
    source.pipe(filter((value, index) => index % n === 0));

/**
 * 因为 pipeable 操作符返回的是函数，还可以进一步简化
 */
const takeEveryNthSimplest = (n) => filter((value, index) => index % n === 0);

interval(100).pipe(
    takeEveryNth(2),
    map(x => x + x),
    takeEveryNthSimple(3),
    map(x => x * x),
    takeEveryNthSimplest(4),
    take(3),
    toArray()
).subscribe(x => console.log(x));

运行代码

node index.js