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# Deprecated APIs#

Node.js may deprecate APIs when either: (a) use of the API is considered to be unsafe, (b) an improved alternative API has been made available, or (c) breaking changes to the API are expected in a future major release.

Node.js utilizes three kinds of Deprecations:

- Documentation-only
- Runtime
- End-of-Life

A Documentation-only deprecation is one that is expressed only within the Node.js API docs. These generate no side-effects while running Node.js.

A Runtime deprecation will, by default, generate a process warning that will be printed to `stderr` the first time the deprecated API is used. When the `--throw-deprecation` command-line flag is used, a Runtime deprecation will cause an error to be thrown.

An End-of-Life deprecation is used to identify code that either has been removed or will soon be removed from Node.js.

## Un-deprecation#

From time-to-time the deprecation of an API may be reversed. Such action may happen in either a semver-minor or semver-major release. In such situations, this document will be updated with information relevant to the decision. However, the deprecation identifier will not be modified.

## List of Deprecated APIs#

### DEP0001: http.OutgoingMessage.prototype.flush#

Type: Runtime

The `OutgoingMessage.prototype.flush()` method is deprecated. Use `OutgoingMessage.prototype.flushHeaders()` instead.

### DEP0002: require('_linklist')#

Type: Runtime

The `_linklist` module is deprecated. Please use a userland alternative.

### DEP0003: _writableState.buffer#

Type: Runtime

The `_writableState.buffer` property is deprecated. Use the `_writableState.getBuffer()` method instead.

### DEP0004: CryptoStream.prototype.readyState#

Type: Documentation-only

The `CryptoStream.prototype.readyState` property is deprecated and should not be used.

### DEP0005: Buffer() constructor#

Type: Documentation-only

The `Buffer()` function and `new Buffer()` constructor are deprecated due to API usability issues that can potentially lead to accidental security issues.

As an alternative, use of the following methods of constructing `Buffer` objects is strongly recommended:

- `Buffer.alloc(size[, fill[, encoding]])` - Create a `Buffer` with initialized memory.
- `Buffer.allocUnsafe(size)` - Create a `Buffer` with uninitialized memory.
- `Buffer.allocUnsafeSlow(size)` - Create a `Buffer` with uninitialized memory.
- `Buffer.from(array)` - Create a `Buffer` with a copy of `array`
- `Buffer.from(arrayBuffer[, byteOffset[, length]])` - Create a `Buffer` that wraps the given `arrayBuffer`.
- `Buffer.from(buffer)` - Create a `Buffer` that copies `buffer`.
- `Buffer.from(string[, encoding])` - Create a `Buffer` that copies `string`.

### DEP0006: child_process options.customFds#

Type: Runtime

Within the `child_process` module's `spawn()`, `fork()`, and `exec()` methods, the `options.customFds` option is deprecated. The `options.stdio` option should be used instead.

### DEP0007: cluster worker.suicide#

Type: Runtime

Within the `cluster` module, the `worker.suicide` property has been deprecated. Please use `worker.exitedAfterDisconnect` instead.

### DEP0008: require('constants')#

Type: Documentation-only

The `constants` module has been deprecated. When requiring access to constants relevant to specific Node.js builtin modules, developers should instead refer to the `constants` property exposed by the relevant module. For instance, `require('fs').constants` and `require('os').constants`.

### DEP0009: crypto.pbkdf2 without digest#

Type: End-of-life

Use of the `crypto.pbkdf2()` API without specifying a digest was deprecated in Node.js 6.0 because the method defaulted to using the non-recommended `'SHA1'` digest. Previously, a deprecation warning was printed. Starting in Node.js 8.0.0, calling `crypto.pbkdf2()` or `crypto.pbkdf2Sync()` with an undefined `digest` will throw a `TypeError`.

### DEP0010: crypto.createCredentials#

Type: Runtime

The `crypto.createCredentials()` API is deprecated. Please use `tls.createSecureContext()` instead.

### DEP0011: crypto.Credentials#

Type: Runtime

The `crypto.Credentials` class is deprecated. Please use `tls.SecureContext` instead.

### DEP0012: Domain.dispose#

Type: Runtime

`Domain.dispose()` is deprecated. Recover from failed I/O actions explicitly via error event handlers set on the domain instead.

### DEP0013: fs asynchronous function without callback#

Type: Runtime

Calling an asynchronous function without a callback is deprecated.

### DEP0014: fs.read legacy String interface#

Type: End-of-Life

The `fs.read()` legacy String interface is deprecated. Use the Buffer API as mentioned in the documentation instead.

### DEP0015: fs.readSync legacy String interface#

Type: End-of-Life

The `fs.readSync()` legacy String interface is deprecated. Use the Buffer API as mentioned in the documentation instead.

### DEP0016: GLOBAL/root#

Type: Runtime

The `GLOBAL` and `root` aliases for the `global` property have been deprecated and should no longer be used.

### DEP0017: Intl.v8BreakIterator#

Type: Runtime

The `Intl.v8BreakIterator` is deprecated and will be removed or replaced soon.

### DEP0018: Unhandled promise rejections#

Type: Runtime

Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

### DEP0019: require('.') resolved outside directory#

Type: Runtime

In certain cases, `require('.')` may resolve outside the package directory. This behavior is deprecated and will be removed in a future major Node.js release.

### DEP0020: Server.connections#

Type: Runtime

The `Server.connections` property is deprecated. Please use the `Server.getConnections()` method instead.

### DEP0021: Server.listenFD#

Type: Runtime

The `Server.listenFD()` method is deprecated. Please use `Server.listen({fd: <number>})` instead.

### DEP0022: os.tmpDir()#

Type: Runtime

The `os.tmpDir()` API is deprecated. Please use `os.tmpdir()` instead.

### DEP0023: os.getNetworkInterfaces()#

Type: Runtime

The `os.getNetworkInterfaces()` method is deprecated. Please use the `os.networkInterfaces` property instead.

### DEP0024: REPLServer.prototype.convertToContext()#

Type: Runtime

The `REPLServer.prototype.convertToContext()` API is deprecated and should not be used.

### DEP0025: require('sys')#

Type: Runtime

The `sys` module is deprecated. Please use the `util` module instead.

### DEP0026: util.print()#

Type: Runtime

The `util.print()` API is deprecated. Please use `console.log()` instead.

### DEP0027: util.puts()#

Type: Runtime

The `util.puts()` API is deprecated. Please use `console.log()` instead.

### DEP0028: util.debug()#

Type: Runtime

The `util.debug()` API is deprecated. Please use `console.error()` instead.

### DEP0029: util.error()#

Type: Runtime

The `util.error()` API is deprecated. Please use `console.error()` instead.

### DEP0030: SlowBuffer#

Type: Documentation-only

The `SlowBuffer` class has been deprecated. Please use `Buffer.allocUnsafeSlow(size)` instead.

### DEP0031: ecdh.setPublicKey()#

Type: Documentation-only

The `ecdh.setPublicKey()` method is now deprecated as its inclusion in the API is not useful.

### DEP0032: domain module#

Type: Documentation-only

The `domain` module is deprecated and should not be used.

### DEP0033: EventEmitter.listenerCount()#

Type: Documentation-only

The `EventEmitter.listenerCount(emitter, eventName)` API has been deprecated. Please use `emitter.listenerCount(eventName)` instead.

### DEP0034: fs.exists(path, callback)#

Type: Documentation-only

The `fs.exists(path, callback)` API has been deprecated. Please use `fs.stat()` or `fs.access()` instead.

### DEP0035: fs.lchmod(path, mode, callback)#

Type: Documentation-only

The `fs.lchmod(path, mode, callback)` API has been deprecated.

### DEP0036: fs.lchmodSync(path, mode)#

Type: Documentation-only

The `fs.lchmodSync(path, mode)` API has been deprecated.

### DEP0037: fs.lchown(path, uid, gid, callback)#

Type: Documentation-only

The `fs.lchown(path, uid, gid, callback)` API has been deprecated.

### DEP0038: fs.lchownSync(path, uid, gid)#

Type: Documentation-only

The `fs.lchownSync(path, uid, gid)` API has been deprecated.

### DEP0039: require.extensions#

Type: Documentation-only

The `require.extensions` property has been deprecated.

### DEP0040: punycode module#

Type: Documentation-only

The `punycode` module has been deprecated. Please use a userland alternative instead.

### DEP0041: NODE_REPL_HISTORY_FILE environment variable#

Type: Documentation-only

The `NODE_REPL_HISTORY_FILE` environment variable has been deprecated.

### DEP0042: tls.CryptoStream#

Type: Documentation-only

The `tls.CryptoStream` class has been deprecated. Please use `tls.TLSSocket` instead.

### DEP0043: tls.SecurePair#

Type: Documentation-only

The `tls.SecurePair` class has been deprecated. Please use `tls.TLSSocket` instead.

### DEP0044: util.isArray()#

Type: Documentation-only

The `util.isArray()` API has been deprecated. Please use `Array.isArray()` instead.

### DEP0045: util.isBoolean()#

Type: Documentation-only

The `util.isBoolean()` API has been deprecated.

### DEP0046: util.isBuffer()#

Type: Documentation-only

The `util.isBuffer()` API has been deprecated. Please use `Buffer.isBuffer()` instead.

### DEP0047: util.isDate()#

Type: Documentation-only

The `util.isDate()` API has been deprecated.

### DEP0048: util.isError()#

Type: Documentation-only

The `util.isError()` API has been deprecated.

### DEP0049: util.isFunction()#

Type: Documentation-only

The `util.isFunction()` API has been deprecated.

### DEP0050: util.isNull()#

Type: Documentation-only

The `util.isNull()` API has been deprecated.

### DEP0051: util.isNullOrUndefined()#

Type: Documentation-only

The `util.isNullOrUndefined()` API has been deprecated.

### DEP0052: util.isNumber()#

Type: Documentation-only

The `util.isNumber()` API has been deprecated.

### DEP0053 util.isObject()#

Type: Documentation-only

The `util.isObject()` API has been deprecated.

### DEP0054: util.isPrimitive()#

Type: Documentation-only

The `util.isPrimitive()` API has been deprecated.

### DEP0055: util.isRegExp()#

Type: Documentation-only

The `util.isRegExp()` API has been deprecated.

### DEP0056: util.isString()#

Type: Documentation-only

The `util.isString()` API has been deprecated.

### DEP0057: util.isSymbol()#

Type: Documentation-only

The `util.isSymbol()` API has been deprecated.

### DEP0058: util.isUndefined()#

Type: Documentation-only

The `util.isUndefined()` API has been deprecated.

### DEP0059: util.log()#

Type: Documentation-only

The `util.log()` API has been deprecated.

### DEP0060: util._extend()#

Type: Documentation-only

The `util._extend()` API has been deprecated.

### DEP0061: fs.SyncWriteStream#

Type: Runtime

The `fs.SyncWriteStream` class was never intended to be a publicly accessible API. No alternative API is available. Please use a userland alternative.

### DEP0062: node --debug#

Type: Runtime

`--debug` activates the legacy V8 debugger interface, which has been removed as of V8 5.8. It is replaced by Inspector which is activated with `--inspect` instead.

### DEP0063: ServerResponse.prototype.writeHeader()#

Type: Documentation-only

The `http` module `ServerResponse.prototype.writeHeader()` API has been deprecated. Please use `ServerResponse.prototype.writeHead()` instead.

Note: The `ServerResponse.prototype.writeHeader()` method was never documented as an officially supported API.

### DEP0064: tls.createSecurePair()#

Type: Runtime

The `tls.createSecurePair()` API was deprecated in documentation in Node.js 0.11.3. Users should use `tls.Socket` instead.

### DEP0065: repl.REPL_MODE_MAGIC and NODE_REPL_MODE=magic#

Type: Documentation-only

The `repl` module's `REPL_MODE_MAGIC` constant, used for `replMode` option, has been deprecated. Its behavior has been functionally identical to that of `REPL_MODE_SLOPPY` since Node.js v6.0.0, when V8 5.0 was imported. Please use `REPL_MODE_SLOPPY` instead.

The `NODE_REPL_MODE` environment variable is used to set the underlying `replMode` of an interactive `node` session. Its default value, `magic`, is similarly deprecated in favor of `sloppy`.

### DEP0066: outgoingMessage._headers, outgoingMessage._headerNames#

Type: Documentation-only

The `http` module `outgoingMessage._headers` and `outgoingMessage._headerNames` properties have been deprecated. Please instead use one of the public methods (e.g. `outgoingMessage.getHeader()`, `outgoingMessage.getHeaders()`, `outgoingMessage.getHeaderNames()`, `outgoingMessage.hasHeader()`, `outgoingMessage.removeHeader()`, `outgoingMessage.setHeader()`) for working with outgoing headers.

Note: `outgoingMessage._headers` and `outgoingMessage._headerNames` were never documented as officially supported properties.

### DEP0067: OutgoingMessage.prototype._renderHeaders#

Type: Documentation-only

The `http` module `OutgoingMessage.prototype._renderHeaders()` API has been deprecated.

Note: `OutgoingMessage.prototype._renderHeaders` was never documented as an officially supported API.

### DEP0068: node debug#

Type: Runtime

`node debug` corresponds to the legacy CLI debugger which has been replaced with a V8-inspector based CLI debugger available through `node inspect`.

### DEP0069: vm.runInDebugContext(string)#

Type: Documentation-only

The DebugContext will be removed in V8 soon and will not be available in Node 10+.

Note: DebugContext was an experimental API.

### DEP0070: async_hooks.currentId()#

Type: Runtime

`async_hooks.currentId()` was renamed to `async_hooks.executionAsyncId()` for clarity.

Note: change was made while `async_hooks` was an experimental API.

### DEP0071: async_hooks.triggerId()#

Type: Runtime

`async_hooks.triggerId()` was renamed to `async_hooks.triggerAsyncId()` for clarity.

Note: change was made while `async_hooks` was an experimental API.

### DEP0072: async_hooks.AsyncResource.triggerId()#

Type: Runtime

`async_hooks.AsyncResource.triggerId()` was renamed to `async_hooks.AsyncResource.triggerAsyncId()` for clarity.

Note: change was made while `async_hooks` was an experimental API.

### DEP0076: tls.parseCertString()#

Type: Documentation-only

`tls.parseCertString()` is a trivial parsing helper that was made public by mistake. This function can usually be replaced with:

    const querystring = require('querystring');
    querystring.parse(str, '\n', '=');

Note: This function is not completely equivalent to `querystring.parse()`. One difference is that `querystring.parse()` does url decoding:

    > querystring.parse('%E5%A5%BD=1', '\n', '=');
    { '好': '1' }
    > tls.parseCertString('%E5%A5%BD=1');
    { '%E5%A5%BD': '1' }

### DEP0079: Custom inspection function on Objects via .inspect()#

Type: Documentation-only

Using a property named `inspect` on an object to specify a custom inspection function for `util.inspect()` is deprecated. Use `util.inspect.custom` instead. For backwards compatibility with Node.js prior to version 6.4.0, both may be specified.