---
title: "indexOf"
description: "Searches for the first occurrence of the substring inside of string. Returns the index of where substring was found, or -1 if it wasn't found."
---

# indexOf

> Searches for the first occurrence of the substring inside of string. Returns the index of where substring was found, or -1 if it wasn't found.

**This function is used by Ignition's Expression language.**

## Description

Searches for the first occurrence of the substring inside of string. Returns the index of where substring was found, or -1 if it wasn't found. The first position in the string is position 0.

## Syntax

`indexOf(string, substring)`

### Parameters

| Type             | Parameter   | Description                                                                                      |
|------------------|-------------|--------------------------------------------------------------------------------------------------|
| String or List   | `string`    | The string to search through. As of version 8.1.8, this parameter also accepts tuples and lists. |
| String           | `substring` | The string to search for.                                                                       |

### Returns

**Integer** - The index where the substring was first found in the string. Returns -1 if the substring is not found.

## Examples

```py title="Code Snippet"
indexOf("Hamburger", "urge") //Returns 4.
```

```py title="Code Snippet"
indexOf("Test", "") //returns 0
```

```py title="Code Snippet"
indexOf("Dysfunctional", "fun") //returns 3
```

```py title="Code Snippet"
indexOf("Dysfunctional", "marble") //returns -1
```

```py title="Code Snippet"
indexOf("banana", "n") //returns 2
```