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JavaScriptBeginner#arrays
slice returns a shallow copy of a range and leaves the original untouched. splice mutates the array by removing and/or inserting elements and returns the removed items.
const a = [1,2,3,4]; a.slice(1,3); // [2,3], a unchanged a.splice(1,2,'x'); // returns [2,3], a is [1,'x',4]