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doc: util.debuglog callback
PR-URL: #33856
Reviewed-By: James M Snell <jasnell@gmail.com>
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bmeck authored and MylesBorins committed Jul 16, 2020
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17 changes: 16 additions & 1 deletion doc/api/util.md
Expand Up @@ -70,13 +70,15 @@ callbackFunction((err, ret) => {
});
```

## `util.debuglog(section)`
## `util.debuglog(section[, callback])`
<!-- YAML
added: v0.11.3
-->

* `section` {string} A string identifying the portion of the application for
which the `debuglog` function is being created.
* `callback` {Function} A callback invoked the first time the logging function
is called with a function argument that is a more optimized logging function.
* Returns: {Function} The logging function

The `util.debuglog()` method is used to create a function that conditionally
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Multiple comma-separated `section` names may be specified in the `NODE_DEBUG`
environment variable: `NODE_DEBUG=fs,net,tls`.

The optional `callback` argument can be used to replace the logging function
with a different function that doesn't have any initialization or
unnecessary wrapping.

```js
const util = require('util');
let debuglog = util.debuglog('internals', (debug) => {
// Replace with a logging function that optimizes out
// testing if the section is enabled
debuglog = debug;
});
```

## `util.deprecate(fn, msg[, code])`
<!-- YAML
added: v0.8.0
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