# Check if a String Contains a Substring in JavaScript

> Use the includes method for a boolean check or indexOf for position-based substring detection in JavaScript, with case-insensitive search options

**URL:** https://sentry.io/answers/string-contains-substring-javascript/

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## The Problem

You want to check whether a string contains a substring in JavaScript. What are the different ways to do this?

## The Solution

There are a number of ways you could approach this problem. We'll take a look at two methods: `includes()` and `indexOf()`.

### The `includes()` method

You can use JavaScript's [`includes()` method](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/includes) to check whether a string contains a substring. This will return `true` if the substring is found, or `false` if not.

Consider the code example below:

```javascript
const str = 'This is my example string!';
const substr = 'my';

console.log(str.includes(substr));
```

The above code would output `true`.

Note that `includes()` performs a case-sensitive search. To work around this, you can convert the string to lower case using `toLowerCase()` as follows:

```javascript
console.log(str.toLowerCase().includes(substr));
```

Furthermore, a `position` can also be passed as an argument to specify the position at which to begin searching the string for the substring. The default position is `0`. If you want to begin searching at position `2`, you would write:

```javascript
console.log(str.includes(substr, 2));
```

### The `indexOf()` method

The `indexOf()` method is also case sensitive, and returns the index position of the first occurrence of the substring within the string. If the substring is not found, it returns `-1`.

```javascript
const str = 'This is my example string!';
const substr = 'my';

console.log(str.indexOf(substr));
```

The code above returns `8`.

You can also include the `position` at which to begin searching the string for the substring. The default position is `0`.

Other search methods you can consider include:

- [`search(regExp)`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/search) – Returns the index of the first match between `regExp` and the string. If no match is found, `-1` is returned.
- [`lastIndexOf(searchValue)`](https://www.w3schools.com/jsref/jsref_lastindexof.asp) – Returns the index position of the last occurrence of `searchValue` inside a string.
- [`match(searchValue)`](https://www.w3schools.com/jsref/jsref_match.asp) – Finds the `searchValue`, a regular expression, within a given string and returns an array containing the matches.
- [`charAt(index)`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/charAt) – Returns a string representing the character at the specified index. If the index is out of range, it returns an empty string.
- [`startsWith(searchValue)`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/startsWith) – Returns `true` or `false` if `searchValue` is found at the beginning of a string.
- [`endsWith(searchValue)`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/endsWith) – Returns `true` or `false` if a string ends with the `searchValue`.

## Further Reading

If you're looking to get a deeper understanding of how [JavaScript application monitoring](https://sentry.io/for/javascript/) works, take a look at the following articles:

- [Making your JavaScript projects less noisy](https://blog.sentry.io/making-your-javascript-projects-less-noisy/)
- [3 Ways to Improve JavaScript Applications](https://blog.sentry.io/3-ways-to-improve-javascript-applications/)
- [JavaScript Debugging Hub](https://sentry.io/answers/javascript/)
- [Sentry for JavaScript](https://docs.sentry.io/platforms/javascript/)
- [JavaScript Error and Performance Monitoring](https://sentry.io/for/javascript/)
- [11 Habits of Highly Effective Developers](https://syntax.fm/show/778/11-habits-of-highly-effective-developers)

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*Source: [sentry.io/answers/string-contains-substring-javascript/](https://sentry.io/answers/string-contains-substring-javascript/)*