1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
import { Observable } from '../Observable';
import { subscribeTo } from '../util/subscribeTo';
import { ObservableInput, SchedulerLike, ObservedValueOf } from '../types';
import { scheduled } from '../scheduled/scheduled';
export function from<O extends ObservableInput<any>>(input: O): Observable<ObservedValueOf<O>>;
/** @deprecated use {@link scheduled} instead. */
export function from<O extends ObservableInput<any>>(input: O, scheduler: SchedulerLike): Observable<ObservedValueOf<O>>;
/**
* Creates an Observable from an Array, an array-like object, a Promise, an iterable object, or an Observable-like object.
*
* <span class="informal">Converts almost anything to an Observable.</span>
*
* 
*
* `from` converts various other objects and data types into Observables. It also converts a Promise, an array-like, or an
* <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#iterable" target="_blank">iterable</a>
* object into an Observable that emits the items in that promise, array, or iterable. A String, in this context, is treated
* as an array of characters. Observable-like objects (contains a function named with the ES2015 Symbol for Observable) can also be
* converted through this operator.
*
* ## Examples
*
* ### Converts an array to an Observable
*
* ```ts
* import { from } from 'rxjs';
*
* const array = [10, 20, 30];
* const result = from(array);
*
* result.subscribe(x => console.log(x));
*
* // Logs:
* // 10
* // 20
* // 30
* ```
*
* ---
*
* ### Convert an infinite iterable (from a generator) to an Observable
*
* ```ts
* import { from } from 'rxjs';
* import { take } from 'rxjs/operators';
*
* function* generateDoubles(seed) {
* let i = seed;
* while (true) {
* yield i;
* i = 2 * i; // double it
* }
* }
*
* const iterator = generateDoubles(3);
* const result = from(iterator).pipe(take(10));
*
* result.subscribe(x => console.log(x));
*
* // Logs:
* // 3
* // 6
* // 12
* // 24
* // 48
* // 96
* // 192
* // 384
* // 768
* // 1536
* ```
*
* ---
*
* ### With async scheduler
*
* ```ts
* import { from, asyncScheduler } from 'rxjs';
*
* console.log('start');
*
* const array = [10, 20, 30];
* const result = from(array, asyncScheduler);
*
* result.subscribe(x => console.log(x));
*
* console.log('end');
*
* // Logs:
* // start
* // end
* // 10
* // 20
* // 30
* ```
*
* @see {@link fromEvent}
* @see {@link fromEventPattern}
*
* @param {ObservableInput<T>} A subscription object, a Promise, an Observable-like,
* an Array, an iterable, or an array-like object to be converted.
* @param {SchedulerLike} An optional {@link SchedulerLike} on which to schedule the emission of values.
* @return {Observable<T>}
* @name from
* @owner Observable
*/
export function from<T>(input: ObservableInput<T>, scheduler?: SchedulerLike): Observable<T> {
if (!scheduler) {
if (input instanceof Observable) {
return input;
}
return new Observable<T>(subscribeTo(input));
} else {
return scheduled(input, scheduler);
}
}