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
|
// @flow strict
import { SYMBOL_ITERATOR } from './symbols';
declare function arrayFrom<T>(arrayLike: Iterable<T>): Array<T>;
// eslint-disable-next-line no-redeclare
declare function arrayFrom<T: mixed>(
arrayLike: mixed,
mapFn?: (elem: mixed, index: number) => T,
thisArg?: mixed,
): Array<T>;
/* eslint-disable no-redeclare */
// $FlowFixMe[name-already-bound]
const arrayFrom =
Array.from ||
function (obj, mapFn, thisArg) {
if (obj == null) {
throw new TypeError(
'Array.from requires an array-like object - not null or undefined',
);
}
// Is Iterable?
const iteratorMethod = obj[SYMBOL_ITERATOR];
if (typeof iteratorMethod === 'function') {
const iterator = iteratorMethod.call(obj);
const result = [];
let step;
for (let i = 0; !(step = iterator.next()).done; ++i) {
result.push(mapFn.call(thisArg, step.value, i));
// Infinite Iterators could cause forEach to run forever.
// After a very large number of iterations, produce an error.
// istanbul ignore if (Too big to actually test)
if (i > 9999999) {
throw new TypeError('Near-infinite iteration.');
}
}
return result;
}
// Is Array like?
const length = obj.length;
if (typeof length === 'number' && length >= 0 && length % 1 === 0) {
const result = [];
for (let i = 0; i < length; ++i) {
if (Object.prototype.hasOwnProperty.call(obj, i)) {
result.push(mapFn.call(thisArg, obj[i], i));
}
}
return result;
}
return [];
};
export default arrayFrom;
|
