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doc: changes to process warning documentation #9590

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Nov 16, 2016
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doc: changes to process warning documentation #9590

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71d4a74
doc: improve process.emitWarning() example
mscdex Nov 13, 2016
5242114
doc: remove redundant warning information
mscdex Nov 13, 2016
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54 changes: 7 additions & 47 deletions doc/api/process.md
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Original file line number Diff line number Diff line change
Expand Up @@ -312,50 +312,6 @@ $ node --no-warnings
The `--trace-warnings` command-line option can be used to have the default
console output for warnings include the full stack trace of the warning.

#### Emitting custom warnings

The [`process.emitWarning()`][process_emit_warning] method can be used to issue
custom or application specific warnings.

```js
// Emit a warning using a string...
process.emitWarning('Something happened!');
// Prints: (node 12345) Warning: Something happened!

// Emit a warning using an object...
process.emitWarning('Something Happened!', 'CustomWarning');
// Prints: (node 12345) CustomWarning: Something happened!

// Emit a warning using a custom Error object...
class CustomWarning extends Error {
constructor(message) {
super(message);
this.name = 'CustomWarning';
Error.captureStackTrace(this, CustomWarning);
}
}
const myWarning = new CustomWarning('Something happened!');
process.emitWarning(myWarning);
// Prints: (node 12345) CustomWarning: Something happened!
```

#### Emitting custom deprecation warnings

Custom deprecation warnings can be emitted by setting the `name` of a custom
warning to `DeprecationWarning`. For instance:

```js
process.emitWarning('This API is deprecated', 'DeprecationWarning');
```

Or,

```js
const err = new Error('This API is deprecated');
err.name = 'DeprecationWarning';
process.emitWarning(err);
```

Launching Node.js using the `--throw-deprecation` command line flag will
cause custom deprecation warnings to be thrown as exceptions.

Expand All @@ -368,6 +324,11 @@ of the custom deprecation.
The `*-deprecation` command line flags only affect warnings that use the name
`DeprecationWarning`.

#### Emitting custom warnings

See the [`process.emitWarning()`][process_emit_warning] method for issuing
custom or application-specific warnings.

### Signal Events

<!--type=event-->
Expand Down Expand Up @@ -821,11 +782,10 @@ so, it is recommended to place the `emitWarning()` behind a simple boolean
flag as illustrated in the example below:

```js
var warned = false;
function emitMyWarning() {
if (!warned) {
if (!emitMyWarning.warned) {
emitMyWarning.warned = true;
process.emitWarning('Only warn once!');
warned = true;
}
}
emitMyWarning();
Expand Down