Function insert

insert<E>(
    array?: null | E[],
    index?: number,
    elements?: null | E[],
): undefined | null | E[]
Returns the array that contains all the given elements at the index of the source array
Type Parameters
- E
Parameters
- Optionalarray: null | E[]
  the array to inspect
- Optionalindex: number
  the index to insert, negative or greater than the length of source array, means at the end of the source array
- Optionalelements: null | E[]
  the elements to insert
Returns undefined | null | E[]
the array that contains all the given elements at the index of the source array
Author
David Hsing
Example
```
insert(['foo', 'bar'], -1, ['hello', 'world']);    // ['foo', 'bar', 'hello', 'world']
insert(['foo', 'bar'], 0, ['hello', 'world']);    // ['hello', 'world', 'foo', 'bar']
insert(['foo', 'bar'], 1, ['hello', 'world']);    // ['foo', 'hello', 'world', 'bar']
insert(['foo', 'bar'], 9, ['hello', 'world']);    // ['foo', 'bar', 'hello', 'world']
```