insertAt

Mutates the original array to insert the given values at the specified index.

Use Array.prototype.splice() with an appropriate index and a delete count of 0, spreading the given values to be inserted.

Note: For immutable array see insertAtImmutable

typescript

const insertAt = (arr: any[], i: number, ...v: any[]) => {
  return [...arr.slice(0, i + 1), ...v, ...arr.slice(i + 1)];
};

typescript

insertAt([1, 2, 3, 4], 2, 5); // [1, 2, 3, 5, 4]
insertAt([2, 10], 0, 4, 6, 8); // [2, 4, 6, 8, 10]

// Insert from behind
insertAt([4, 5], -1, 1, 2, 3); // [1, 2, 3, 4, 5]