Node.js APIs differences
We support the majority of Node.js upstream APIs, see the official docs.
However, some Node.js APIs were designed with the purpose of running on a server/desktop environment, and on mobile they might not work as intended or are not supported at all.
This page contains a collection of differences for these APIs when running on a mobile environment or a description of the quirks in their behavior. Please file an issue in the core library repo for APIs that you find missing from the list.
Child processes
Unsupported
The child_process and cluster modules are not available. nodejs-mobile runs in a mobile application process, which is expected to be a single process in the mobile operating systems, so forking the nodejs-mobile process results in errors for most cases. iOS doesn't give permissions to spawn new processes in most cases, as well. These modules are not supported in nodejs-mobile for the reasons presented.
Console
Supported, with minor differences
The global console instance is typically configured to write to process.stdout and process.stderr. On Android, the process.stderr and process.stdout streams output is sent to /dev/null, but it can be redirected to the application logcat. The redirection is done automatically in the nodejs-mobile-cordova and nodejs-mobile-react-native plugins. Instructions on how to achieve this in Android applications running the native nodejs-mobile library can be found in the Android Redirect Output Streams to logcat guide.
Debugger
Unsupported
The V8 inspector is not available on current nodejs-mobile builds, due to a dependency on the intl module. This means you cannot use (Chrome) DevTools to debug your nodejs-mobile app.
File system module
Supported, with significant differences
The fs module provides wrappers around standard POSIX functions, but these might not be available on the mobile OSes, file systems or work differently in a mobile application process context.
Functions that can take relative paths apply that relative path to the current working directory where the node process was started in server/desktop environments. On mobile environments, nodejs-mobile is started in the context of an application, for which the current working environment is the root of the filesystem on iOS and Android. This can lead to unexpected behavior for code that assumes the current working directory is set to the directory of the starting Node.js script (which also might not be true in a server/desktop environment).
fs.link(), fs.linkSync()
Android does not support these functions because it does not support hard links.
Internationalization module
Unsupported
The intl (internationalization) module is not available on current nodejs-mobile builds.
Operation system module
Supported, with significant differences
The os module provides operating system-related utility methods. Some of these methods are not fully supported on mobile operating systems or behave differently in the context of an application process.
os.cpus()
On iOS, CPU speed values are always 0, due to lack of permissions to read these values.
On Android, returns undefined since Android 8.0, due to lack of permissions to read these values. On earlier Android versions the CPU values can be inconsistent, since some devices can turn CPU cores on and off as an energy saving strategy. Properties can be returned as zero for cores that have been turned off while getting them.
os.homedir()
On Android and iOS there isn't the concept of a user home directory. Android sets this value to /data and iOS sets it to root of the Application's sandboxed path.
os.platform()
Returns the strings 'android' or 'ios' in nodejs-mobile, depending on the platform.
os.tmpdir()
On iOS, returns the application's sandboxed temporary directory, equivalent to getting the NSTemporaryDirectory value, since iOS sets the TMPDIR environment variable for the application to that value.
The Android OS is an outlier in the sense that it doesn't have the concept of a temporary directory. In the nodejs-mobile-cordova and nodejs-mobile-react-native plugins, the nodejs-mobile runtime returns the application context's CacheDir value, which should have a similar behavior to a temporary directory for most situations (on Android, the files in the cache are kept until the system needs space, so it increases the disk foothold of the Application unless the developer deletes them manually).
Process
Supported, with significant differences
The global process object provides information about the current process where Node.js is running on, which is the application process for nodejs-mobile.
process.cwd()
The current working directory of the process is the same as the current working directory for the mobile application, which is the root of the operating system on Android and iOS applications, i.e. /.
process.exit()
In nodejs-mobile, the process is the application, so running process.exit() terminates the application. This is not allowed in the Apple App Store guidelines for iOS.
process.getegid(), process.geteuid(), process.getgid(), process.getgroups(), process.getuid(), process.setegid(), process.seteuid(), process.setgid(), process.setgroups(), process.setuid()
These functions are only available on POSIX platforms, so they are unavailable on Android.
process.stderr, process.stdout
Read above in the Console section.
process.stdin
nodejs-mobile is running in the context of a mobile application, so you can expect process.stdin to be unavailable unless there is some native code added to pipe to it.
process.platform
Like os.platform(), this is the string 'android' or 'ios', depending on the platform.
process.versions
The process.versions object is supported, but also includes the 'mobile' key, containing the version for the nodejs-mobile core library.
RegExp Unicode Property Names
Unsupported
Nodejs-mobile is compiled with no internationalization which means that Unicode Property Names are not supported, examples:
\p{Letter}\p{L}\p{ID_Start}\p{ID_Continue}
As an alternative, you can unwrap the characters belonging to property names, like this:
const regenerate = require('regenerate');
const codePoints = require('@unicode/unicode-13.0.0/Binary_Property/ID_Start/code-points.js');
const set = regenerate(codePoints);
console.log(new RegExp(`[$_${set.toString()}]`));
Or do such as a dedicated package, like unicode-word-regex does.
WebAssembly
Unsupported
On iOS, WASM is unsupported because it requires Just-in-time (JIT) interpretation, which is forbidden by Apple's App Store guidelines.
On Android, WASM may work.