Certainly! Here's an example of a function that creates a 2D grid of null elements based on the specified number of rows and columns:


```typescript
function createGrid(rows: number, columns: number): null[][] {
  const grid: null[][] = [];

  for (let i = 0; i < rows; i++) {
    const row: null[] = [];
    
    for (let j = 0; j < columns; j++) {
      row.push(null);
    }

    grid.push(row);
  }

  return grid;
}

const rows = 3;
const columns = 4;
const grid = createGrid(rows, columns);

console.log(grid);

```

In this example, the `createGrid` function accepts two parameters - `rows` and `columns`, representing the desired number of rows and columns in the grid.

The function initializes an empty `grid` array and then uses nested loops to create the rows and fill them with null values. The outer loop iterates `rows` times, while the inner loop iterates `columns` times, pushing null elements into each row.

Finally, the created grid is returned and printed to the console.

You can adjust the `rows` and `columns` variables with the desired values to create a grid of the desired size.

Let me know if you need any further assistance or have any other questions!