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Fix: fallback to typeof when toString is applied to incompatible object #16017

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merged 1 commit into from Oct 10, 2023
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Fix: fallback to typeof when toString is applied to incompatible object #16017

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7 changes: 6 additions & 1 deletion packages/babel-helpers/src/helpers.ts
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Expand Up @@ -314,7 +314,12 @@ helpers.construct = helper("7.0.0-beta.0")`
helpers.isNativeFunction = helper("7.0.0-beta.0")`
export default function _isNativeFunction(fn) {
// Note: This function returns "true" for core-js functions.
return Function.toString.call(fn).indexOf("[native code]") !== -1;
try {
return Function.toString.call(fn).indexOf("[native code]") !== -1;
} catch (e) {
// Firefox 31 throws when "toString" is applied to an HTMLElement
return typeof fn === "function";
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This is safe because on user-defined Function.toString never throws, right?

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I think so, Function.toString will throw a type error if the input is neither object nor function, unless there are more browser quirks we are unaware of.

According to this SO issue, Function.toString throws on HTMLElement because at that time they were not inherited from Object.

}
}
`;

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