function default.ifError
Usage in Deno
```typescript import mod from "node:node__assert.d.ts"; ```
ifError(value: unknown): asserts value is null | undefined
Throws `value` if `value` is not `undefined` or `null`. This is useful when
testing the `error` argument in callbacks. The stack trace contains all frames
from the error passed to `ifError()` including the potential new frames for `ifError()` itself.
```js
import assert from 'node:assert/strict';
assert.ifError(null);
// OK
assert.ifError(0);
// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: 0
assert.ifError('error');
// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: 'error'
assert.ifError(new Error());
// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: Error
// Create some random error frames.
let err;
(function errorFrame() {
err = new Error('test error');
})();
(function ifErrorFrame() {
assert.ifError(err);
})();
// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: test error
// at ifErrorFrame
// at errorFrame
```
asserts value is null | undefined