Last change
on this file since 6c1585f was 6a3a178, checked in by Ema <ema_spirova@…>, 3 years ago |
initial commit
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100644
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File size:
1.3 KB
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[6a3a178] | 1 | 'use strict';
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| 2 |
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| 3 | Object.defineProperty(exports, "__esModule", {
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| 4 | value: true
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| 5 | });
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| 6 | exports['default'] = symbolObservablePonyfill;
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| 7 | function symbolObservablePonyfill(root) {
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| 8 | var result;
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| 9 | var _Symbol = root.Symbol;
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| 10 |
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| 11 | if (typeof _Symbol === 'function') {
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| 12 | if (_Symbol.observable) {
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| 13 | result = _Symbol.observable;
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| 14 | } else {
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| 15 |
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| 16 | if (typeof _Symbol['for'] === 'function') {
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| 17 | // This just needs to be something that won't trample other user's Symbol.for use
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| 18 | // It also will guide people to the source of their issues, if this is problematic.
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| 19 | // META: It's a resource locator!
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| 20 | result = _Symbol['for']('https://github.com/benlesh/symbol-observable');
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| 21 | } else {
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| 22 | // Symbol.for didn't exist! The best we can do at this point is a totally
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| 23 | // unique symbol. Note that the string argument here is a descriptor, not
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| 24 | // an identifier. This symbol is unique.
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| 25 | result = _Symbol('https://github.com/benlesh/symbol-observable');
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| 26 | }
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| 27 | try {
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| 28 | _Symbol.observable = result;
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| 29 | } catch (err) {
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| 30 | // Do nothing. In some environments, users have frozen `Symbol` for security reasons,
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| 31 | // if it is frozen assigning to it will throw. In this case, we don't care, because
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| 32 | // they will need to use the returned value from the ponyfill.
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| 33 | }
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| 34 | }
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| 35 | } else {
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| 36 | result = '@@observable';
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| 37 | }
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| 38 |
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| 39 | return result;
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| 40 | }; |
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