Development Tips

Resolving Permission Errors

EACCES permission errors can occur when packages are installed globally. If this is the case, npm may need to be set up to operate without elevated permissions.

注記

Using sudo with npm is not recommended because it can lead to further complications.

This guide offers two options for resolving permission issues. See the npm docs for full documentation and additional options.

Option 1

The best way to avoid permission issues is to reinstall NodeJS and npm using a node version manager.

This guide will document nvm installation and usage. See the nvm docs for full documentation. See the npm docs for additional options and instructions for Windows.

1. Install nvm.

   $ curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.34.0/install.sh | bash

2. New terminals will now use nvm. To verify, open a new terminal and run the following. If something prints, the installation was successful.

   $ command -v nvm

3. To download and install the latest LTS release of NodeJS, run:

   $ nvm install --lts

4. Set the newly installed NodeJS as the default environment:

   $ nvm alias default lts/*

5. New terminals will now use the nvm-controlled NodeJS. To verify:

   $ node -v  # will print the version installed above
   $ which npm  # will print a path somewhere within the ~/.nvm folder

Global packages will now be installed in the ~/.nvm directory, so permission errors should no longer occur as long as npm is used without sudo.

Option 2

Does not apply to Windows

Change the owner of npm's directories to the current user:

$ sudo chown -R $(whoami) /usr/local/{lib/node_modules,bin,share}
$ sudo chown -R $(whoami) /usr/lib/node_modules
$ sudo chown -R $(whoami) ~/.npm ~/.npmrc

Since these global directories are no longer owned by root, packages can be installed globally without sudo.

Updating Dependencies

To update an npm dependency, run the following, where <package-name> is the package to update:

npm install <package-name>@<version|latest> --save

For example, to update the @ionic/angular package to the release tagged latest, run:

npm install @ionic/angular@latest --save

It is recommended that packages get updated through the CLI since npm will now read package versions from the package-lock.json first.

Code Editors

There are a lot of code editors to choose from. Here are some of our favorites:

• Visual Studio Code: a popular and free text editor made by Microsoft
• Atom: a hackable text editor made by GitHub
• WebStorm: a powerful non-free editor by JetBrains

Using a Debugger

The debugger keyword can be used to debug an app. When most browsers encounters a debugger statement, running of JavaScript is stopped, and the browser will load its debugger. This can be used to set "breakpoints" in the app.

For example, if a function is not returning the correct value, the debugger can be used to step through the code and inspect variables.

function myBrokenFunction() {
  debugger;
  // do other stuff
}

When an app runs, it will pause at this function. From there, the developer tools can be used to run pieces of JavaScript, line by line, and inspect where exactly the function breaks.

Changing Mode

By default, when an app is viewed in the browser, Ionic will apply the md mode. However, since Ionic components adapt according to their platform, it is helpful to be able to view what the app will look like on iOS. To do this, add ?ionic:mode=ios to the URL where the app is being served. For example, if the app is served on port 8100, the url would be: http://localhost:8100/?ionic:mode=ios.

注記

This will not change which platform the browser sees being used. The platform is determined by device detection and inspecting the user-agent. To change the platform, the user-agent must be changed. To do this, open up Chrome DevTools with Ctrl+Shift+I(Cmd+Option+I on Mac), and then toggle device mode on with Ctrl+Shift+M(Cmd+Option+M on Mac).

Selecting devices from the device dropdown will change the user-agent, as well as the dimensions of the viewport.

Using the iOS Simulator

The iOS simulator enables testing and debugging of an app before it reaches an actual device.

Before it can be used, Xcode, Apple's IDE, must be installed.

The Ionic CLI can then be used to run the app in the current directory on the simulator:

ionic cordova emulate ios -lc

Passing in the -lc flag will enable livereload and log console output to a terminal.

Xcode can also be used to launch the emulator and debug an app.

Open up Xcode and open ../path-to-app/platforms/ios/myApp.xcodeproj.

After the app loads, console output and device logs will be printed inside of Xcode's output window.

Using the Genymotion Android Emulator

While the Android SDK comes with a stock emulator, it can be slow and unresponsive at times.

Genymotion is an alternate emulator that is faster, and still allows access to native functionality like GPS and camera.