The flat function for JavaScript Arrays is not defined in React Native

I am currently developing an application using react-native and it's common knowledge that we can utilize JavaScript code in this particular project as well as any other react projects.

However, whenever I attempt to use the following code snippet, the transpiler throws an Error when running on the simulator:

const mixer = (...arg) => arg.flat(9);

The error message reads: flat is not a function

Can anyone explain why this works perfectly fine in a browser environment but fails in react-native? Thank you!

javascriptarraysreact-native

Answer №1

React Native utilizes the JavaScriptCore engine, which follows the ECMA-262 specification. The specification clearly states that the .flat method is not supported and is not included in babel's list of transformations.

To address this issue, you can either create your own implementation or install one of the numerous shims available on npm.

Answer №2

Don't just rely on arr.flat, give this handy function a try instead:

function flattenArray(arr) {
    return Array.prototype.concat(...arr);
}

flattenArray(arr)

Answer №3

Does your platform support this feature? Check out Array.prototype.flat

You can also find alternative implementations using reduce and concat methods, as well as non-recursive solutions.

Answer №4

const mixer = (...arg) => arg.flat(9);

An issue arises: flat is not function

How come react-native does not recognize it while it works fine in the browser?

One possibility is that the react-native transpiler is misinterpreting your ...arg, resulting in an object that is not of type Array. By trying to use .flat, which belongs to Array.prototype, the code fails since arg might not be considered as an array, thus causing the error.

Although not confirmed, you can verify the object type using the following temporary snippet.

const mixer = (...arg) => { console.log(typeof arg); return []; }

What does it output? If it indicates Array, then it's possible that the platform doesn't support the function yet. Utilizing a polyfill could resolve this issue.

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