More JS. slice()

Further Study: Negative index in slice()

• start parameter can take negative index value, which means it starts from the end. slice(-2) will extract last two elements in the sequence.
  

• end parameter can also take negative index value, meaning that it starts from the end of the sequence. slice(2, -1) will extract the third element through the second-to-last element in the sequence.

const animals = ['ant', 'bison', 'camel', 'duck', 'elephant', 'falcon'];

/* starts from index 1,
  count 2 elements from the end(excluded) */
console.log(animals.slice(1, -2));
// ['bison', 'camel', 'duck']

console.log(animals.slice(2, -1));
// (3) ['camel', 'duck', 'elephant']

console.log(animals.slice(2, -3));
// ['camel']

To separate an array - all elements without last element and the last element - Use arr.slice(0, -1) and arr.slice(-1) ( arr[arr.length - 1] would also work).