RxJS Observable 创建操作符详解：从 create 到 timer

// RxJS v6+
import { Observable } from 'rxjs';
/*
  创建在订阅函数中发出 'Hello' 和 'World' 的 observable 。
*/
const hello = Observable.create(function(observer) {
  observer.next('Hello');
  observer.next('World');
});

// 输出: 'Hello'...'World'
const subscribe = hello.subscribe(val => console.log(val));

var source = Rx.Observable.empty();

source.subscribe({
    next: function(value) {
        console.log(value)
    },
    complete: function() {
        console.log('complete!');
    },
    error: function(error) {
        console.log(error)
    }
});
// complete!

// RxJS v6+
import { from } from 'rxjs';

// 将数组作为值的序列发出
const arraySource = from([1, 2, 3, 4, 5]);
// 输出: 1,2,3,4,5
const subscribe = arraySource.subscribe(val => console.log(val));

// RxJS v6+
import { of } from 'rxjs';

// 依次发出提供的任意数量的值
const source = of(1, 2, 3, 4, 5);
// 输出: 1,2,3,4,5
const subscribe = source.subscribe(val => console.log(val));

​​fromEvent​​ 将事件转换成 observable 序列；

// RxJS v6+
import { fromEvent } from 'rxjs';
import { map } from 'rxjs/operators';

// 创建发出点击事件的 observable
const source = fromEvent(document, 'click');
// 映射成给定的事件时间戳
const example = source.pipe(map(event => `Event time: ${event.timeStamp}`));
// 输出 (示例中的数字以运行时为准): 'Event time: 7276.390000000001'
const subscribe = example.subscribe(val => console.log(val));

var source = Rx.Observable
  .fromPromise((resolve, reject) => {
    setTimeout(() => {
      resolve('Hello RxJS!');
    },3000)
  })

// 等同于
var source = Rx.Observable
  .from(new Promise((resolve, reject) => {
    setTimeout(() => {
      resolve('Hello RxJS!');
    },3000)
  }))

// RxJS v6+
import { interval } from 'rxjs';

// 每1秒发出数字序列中的值
const source = interval(1000);
// 数字: 0,1,2,3,4,5....
const subscribe = source.subscribe(val => console.log(val));

// import { interval } from 'rxjs';
// const source = interval(1000);
// 等同于
// var source = Rx.Observable.interval(1000);

// RxJS v6+
import { timer } from 'rxjs';

/*
  timer 接收第二个参数，它决定了发出序列值的频率，在本例中我们在1秒发出第一个值，
  然后每2秒发出序列值
*/
const source = timer(1000, 2000);
// 输出: 0,1,2,3,4,5......
const subscribe = source.subscribe(val => console.log(val));