> ## Documentation Index
> Fetch the complete documentation index at: https://new.docs.falkordb.com/llms.txt
> Use this file to discover all available pages before exploring further.

# text.indexOf

> Finds the index of the first occurrence of a substring in a string, with optional range constraints.

## Description

Finds the first occurrence of a substring within a string, optionally starting from a specific offset and ending at a specific position.

## Syntax

```cypher theme={null}
flex.text.indexOf(string, substring, offset, to)
```

## Parameters

| Parameter   | Type   | Required | Description                                                     |
| ----------- | ------ | -------- | --------------------------------------------------------------- |
| `string`    | string | Yes      | The string to search in                                         |
| `substring` | string | Yes      | The substring to search for                                     |
| `offset`    | number | No       | Starting position for search (default: 0)                       |
| `to`        | number | No       | Ending position for search (default: -1, meaning end of string) |

## Returns

**Type:** number (integer)

The zero-based index of the first occurrence of the substring, or `-1` if not found. Returns `null` if the input string is `null`.

## Examples

### Example 1: Basic Search

```cypher theme={null}
RETURN flex.text.indexOf('hello world', 'world') AS position
```

**Output:**

```text theme={null}
position
--------
6
```

### Example 2: Search with Offset

```cypher theme={null}
RETURN flex.text.indexOf('hello hello', 'hello', 3) AS position
```

**Output:**

```text theme={null}
position
--------
6
```

(Finds the second "hello" starting from position 3)

### Example 3: Filtering Nodes by Substring Position

```cypher theme={null}
MATCH (p:Product)
WHERE flex.text.indexOf(p.description, 'premium') >= 0
RETURN p.name, p.description
```

## Notes

* Returns `null` if input string is `null`
* Returns `-1` if substring is not found
* Uses zero-based indexing
* The `offset` parameter allows starting search from a specific position
* The `to` parameter limits search to a specific range

## See Also

* [text.indexesOf](/udfs/flex/text/indexesOf) - Find all occurrences of a substring
* [text.replace](/udfs/flex/text/replace) - Replace substring occurrences

## Frequently Asked Questions

<AccordionGroup>
  <Accordion title="What does flex.text.indexOf return if the substring is not found?">
    It returns `-1` when the substring is not present in the search range.
  </Accordion>

  <Accordion title="Is the search case-sensitive?">
    Yes. The search is case-sensitive. Use `toLower()` on both strings if you need case-insensitive matching.
  </Accordion>
</AccordionGroup>