var example = ['A', 'B', 'C', 'D'];

example.splice(2, 0, 'E');       // remove 0 item, and insert 'E' at 2-index

console.log(example);
// ["A", "B", "E", "C", "D"]
var copy = example.splice(2, 1); // remove 1 item at 2-index postion, return the deleted item

console.log(copy);
// ["E"]
console.log(example);
// ["A", "B", "C", "D"]
var copy2 = example.splice(2, 0, 'E');

console.log(copy2);
// []
console.log(example);
// ["A", "B", "E", "C", "D"]