Use arr.reverse() to reverse an array in place. To get the reversed order without changing the original array, use arr.toReversed() where the runtime supports it, or reverse a shallow copy with [...arr].reverse().
Reverse an array in place with reverse()
reverse() changes the array it is called on and returns that same array reference:
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const values = [1, 2, 3];
const result = values.reverse();
console.log(values); // [3, 2, 1]
console.log(result === values); // trueBecause it mutates the original, any other variable referring to values sees the reversed order too. Assigning the return value to a new variable does not preserve the old array.
Keep the original order
Use toReversed() when supported
toReversed() returns a new array in reverse order and leaves the input array’s order unchanged:
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const values = [1, 2, 3];
const reversed = values.toReversed();
console.log(reversed); // [3, 2, 1]
console.log(values); // [1, 2, 3]TypeScript includes the method’s declaration in its ES2023 library APIs. The lib option controls which built-in declarations the compiler recognizes, but declarations do not add a method to the JavaScript runtime. Check both your TypeScript configuration and the runtime where the code will execute; a successful type check alone does not guarantee that toReversed() exists there. See the TypeScript TSConfig lib reference and MDN’s toReversed() documentation.
Copy first for broader runtime compatibility
Make a shallow copy, then reverse that copy:
const values = [1, 2, 3];
const reversed = [...values].reverse();
// Alternative: values.slice().reverse()The spread and slice() forms leave the original array’s order intact. Choose the expression that matches your mutation needs: reverse() for an in-place change, and toReversed() or copy-then-reverse for a separate result.
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Readonly arrays and shallow copies
A value typed as readonly T[] cannot be mutated through that readonly type, so calling reverse() on it is not allowed by TypeScript. Copy it first to get a mutable array, for example with [...items].reverse(). toReversed() is also non-mutating when its declaration and runtime support are available. TypeScript describes ReadonlyArray as a type for arrays that should not be changed in its Object Types handbook.
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Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallThese copy-based approaches make a new outer array, not a deep copy of its elements. If the array contains objects, the original and reversed arrays still refer to the same objects. MDN explains this in its Array reference.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How sparse arrays behave
If an array contains empty slots, the methods handle them differently: reverse() preserves empty slots in their reversed positions, while toReversed() reads those holes as undefined and returns a dense array at those positions. For ordinary dense arrays of primitives, both approaches produce the expected reversed order. More detail is available in the MDN references for reverse() and toReversed().
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