# Built-in utilities
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The `util` variable contains general utility methods to help you work with data. Unless otherwise specified, all utilities use the UTF-8 character set.

## Encoding utils
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### Encoding utils list
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 **`util.urlEncode(String)`**  
Returns the input string as an `application/x-www-form-urlencoded` encoded string.

 **`util.urlDecode(String)`**  
Decodes an `application/x-www-form-urlencoded` encoded string back to its non-encoded form.

**`util.base64Encode(string) : string`**  
Encodes the input into a base64-encoded string.

**`util.base64Decode(string) : string`**  
Decodes the data from a base64-encoded string.

## ID generation utils
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### ID generation utils list
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 **`util.autoId()`**  
Returns a 128-bit randomly generated UUID.

**`util.autoUlid()`**  
Returns a 128-bit randomly generated ULID (Universally Unique Lexicographically Sortable Identifier).

**`util.autoKsuid()`**  
Returns a 128-bit randomly generated KSUID (K-Sortable Unique Identifier) base62 encoded as a String with a length of 27.

## Error utils
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### Error utils list
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 **`util.error(String, String?, Object?, Object?)`**  
Throws a custom error. This can be used in request or response mapping templates if the template detects an error with the request or with the invocation result. Additionally, an `errorType` field, a `data` field, and an `errorInfo` field can be specified. The `data` value will be added to the corresponding `error` block inside `errors` in the GraphQL response.  
`data` will be filtered based on the query selection set. The `errorInfo` value will be added to the corresponding `error` block inside `errors` in the GraphQL response.  
`errorInfo` will **not** be filtered based on the query selection set.

 **`util.appendError(String, String?, Object?, Object?)`**  
Appends a custom error. This can be used in request or response mapping templates if the template detects an error with the request or with the invocation result. Additionally, an `errorType` field, a `data` field, and an `errorInfo` field can be specified. Unlike `util.error(String, String?, Object?, Object?)`, the template evaluation will not be interrupted, so that data can be returned to the caller. The `data` value will be added to the corresponding `error` block inside `errors` in the GraphQL response.  
`data` will be filtered based on the query selection set. The `errorInfo` value will be added to the corresponding `error` block inside `errors` in the GraphQL response.  
`errorInfo` will **not** be filtered based on the query selection set.

## Type and pattern matching utils
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### Type and pattern matching utils list
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**`util.matches(String, String) : Boolean`**  
Returns true if the specified pattern in the first argument matches the supplied data in the second argument. The pattern must be a regular expression such as `util.matches("a*b", "aaaaab")`. The functionality is based on [Pattern](https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html), which you can reference for further documentation.

 **`util.authType()`**   
Returns a String describing the multi-auth type being used by a request, returning back either "IAM Authorization", "User Pool Authorization", "Open ID Connect Authorization", or "API Key Authorization".

## Return value behavior utils
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### Return value behavior utils list
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 **`util.escapeJavaScript(String)`**  
Returns the input string as a JavaScript escaped string.

## Resolver authorization utils
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### Resolver authorization utils list
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 **`util.unauthorized()`**  
Throws `Unauthorized` for the field being resolved. Use this in request or response mapping templates to determine whether to allow the caller to resolve the field.