Function isDefined

isDefined(val: unknown): val is {}
Checks if value is specifically not undefined.

Inverse of isUndefined. Returns true for all values except undefined, including null, false, 0, and empty strings.
Parameters
- val: unknown
  value to check
Returns val is {}
true if value is not undefined
Example
```
isDefined(null) // true
isDefined(0) // true
isDefined('') // true
isDefined(false) // true
isDefined(undefined) // false

const config = getConfig();
if (isDefined(config.apiKey)) {
    // Safe to use config.apiKey
}
```
- Defined in packages/utils/src/validation/type-guards.ts:283