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34 lines
1.2 KiB
34 lines
1.2 KiB
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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