slice is an option to make a shallow copy.

another modern way (ES6) is Array.from(age) o with spread [...ages]

Nothing says the inmutability of age needs to be preserved. Actually it doesn't.

@mreza-dehghani: you can use a slice to preserve the original array: _data = ages.slice().sort(...

so what is your solution??

Array.sort makes in-place operations so inmutability of ages array is not guaranteed. It implies having side effects after executing function.