JS Array - Slice vs Splice

JavaScript Array Slice vs Splice: the Difference Explained with CakefreeCodeCamp.org

Slice => copies a slice of the array and returns the copies slice (org. array remains unmutated)

Splice => plucks out(removes) a slice from the array and returns the remaining array, can also be used add elements to the array

For both:

start

Negative index counts back from the end of the array — if start < 0, start + array.length is used.

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end

Negative index counts back from the end of the array — if end < 0, end + array.length is used.