```

Copy this code and paste it in the editor, then hit `Run` and `Save and Close`. As you might have guessed, this puts a block on the coordinates `(0, 0, 0)`. The fourth value is the unique identifier for the Grass block to be placed. There is a list of unique ids for each built-in block, but what if we want to place a custom block instead?

We have already seen some built-in functions, but what if we wanted to create our own ones?

```js

function moveBlock(fromX, fromY, fromZ, toX, toY, toZ) {

```

This time, the line starts with a `for` loop expression. Inside this expression, we create a variable `index` and assign it to each index in the array. The code inside the curly braces will then be repeated for each new index. This is similar to using a [[Loop]] block with the array length as input.

```js

// Create an empty object

let myBlocks = {};