---
title: "JSValueToUInt64(_:_:_:)"
framework: JavaScriptCore
role: symbol
role_heading: Function
platforms: [iOS 18.0+, iPadOS 18.0+, Mac Catalyst 18.0+, macOS 15.0+, tvOS 9.0+, visionOS 2.0+]
path: "javascriptcore/jsvaluetouint64(_:_:_:)"
---

# JSValueToUInt64(_:_:_:)

## Declaration

```swift
func JSValueToUInt64(_ ctx: JSContextRef, _ value: JSValueRef, _ exception: UnsafeMutablePointer<JSValueRef?>?) -> UInt64
```

## Parameters

- `ctx`: The execution context to use.
- `value`: The JSValue to convert.
- `exception`: A pointer to a JSValueRef in which to store an exception, if any. To reliable detect exception, initialize this to null before the call. Pass NULL if you do not care to store an exception.

## Return Value

Return Value A uint64_t with the result of conversion, or 0 if an exception is thrown. Since 0 is valid value, exception must be checked after the call.

## Discussion

Discussion Converts a JSValue to an unsigned 64-bit integer and returns the resulting integer. The JSValue is converted to an integer according to the rules specified by the JavaScript language. If the value is a BigInt, then the JSValue is truncated to a uint64_t.