# INDEX\_OF

### Description

`INDEX_OF` returns the zero-based index of the first occurrence of a value in a list or string. If the value is not found, it returns `-1`.

### Syntax

```
INDEX_OF(collection, value)
```

**Returns:** An integer index, or `-1` if not found.

### Example with a list

```
INDEX_OF(['red', 'green', 'blue'], 'green')
```

This returns `1`, since `'green'` is at index 1 (zero-based).

### Example with a string

```
INDEX_OF('Hello World', 'World')
```

This returns `6`, the position where `'World'` begins.

### Example when not found

```
INDEX_OF(['a', 'b', 'c'], 'z')
```

This returns `-1`.


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