35 lines
1.2 KiB
JavaScript
35 lines
1.2 KiB
JavaScript
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export default function symbolObservablePonyfill(root) {
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var result;
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var Symbol = root.Symbol;
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if (typeof Symbol === 'function') {
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if (Symbol.observable) {
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result = Symbol.observable;
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} else {
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if (typeof Symbol.for === 'function') {
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// This just needs to be something that won't trample other user's Symbol.for use
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// It also will guide people to the source of their issues, if this is problematic.
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// META: It's a resource locator!
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result = Symbol.for('https://github.com/benlesh/symbol-observable');
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} else {
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// Symbol.for didn't exist! The best we can do at this point is a totally
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// unique symbol. Note that the string argument here is a descriptor, not
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// an identifier. This symbol is unique.
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result = Symbol('https://github.com/benlesh/symbol-observable');
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}
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try {
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Symbol.observable = result;
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} catch (err) {
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// Do nothing. In some environments, users have frozen `Symbol` for security reasons,
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// if it is frozen assigning to it will throw. In this case, we don't care, because
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// they will need to use the returned value from the ponyfill.
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}
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}
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} else {
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result = '@@observable';
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}
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return result;
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};
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