let arr = ['foo', 'bar', 10, 'qux'];
// arr.splice(<index>, <steps>, [elements ...]);
arr.splice(1, 1); // Removes 1 item at index 1
// => ['foo', 10, 'qux']
arr.splice(2, 1, 'tmp'); // Replaces 1 item at index 2 with 'tmp'
// => ['foo', 10, 'tmp']
arr.splice(0, 1, 'x', 'y'); // Inserts 'x' and 'y' replacing 1 item at index 0
// => ['x', 'y', 10, 'tmp']