Pop vs Push & Shift vs Unshift

pop(): Remove an item from the end of an array

let cats = ['Bob', 'Willy', 'Mini'];

cats.pop(); // ['Bob', 'Willy']

pop() returns the removed item.

push(): Add items to the end of an array

let cats = ['Bob'];

cats.push('Willy'); // ['Bob', 'Willy']

cats.push('Puff', 'George'); // ['Bob', 'Willy', 'Puff', 'George']

push() returns the new array length.

shift(): Remove an item from the beginning of an array

let cats = ['Bob', 'Willy', 'Mini'];

cats.shift(); // ['Willy', 'Mini']

shift() returns the removed item.

unshift(): Add items to the beginning of an array

let cats = ['Bob'];

cats.unshift('Willy'); // ['Willy', 'Bob']

cats.unshift('Puff', 'George'); // ['Puff', 'George', 'Willy', 'Bob']

unshift() returns the new array length.