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Learn how to use the Expo Build lifecycle hooks with npm to customize your build process.

Expo Build lifecycle npm hooks allows you to customize your build process by running scripts before or after the build process.

For better understanding, see the Android build process and the iOS build process.

The lifecycle hooks are not executed by the build process in custom builds. They need to be manually extracted and called by the build steps during the process.

Expo Build lifecycle hooks

There are six Expo Build lifecycle npm hooks available. To use, them, you can set them in your package.json.

An example of how a package.json can look when using one or more lifecycle hooks:

{
  "name": "my-app",
  "scripts": {
    "eas-build-pre-install": "echo 123",
    "eas-build-post-install": "echo 456",
    "eas-build-on-success": "echo 789",
    "eas-build-on-error": "echo 012",
    "eas-build-on-cancel": "echo 345",
    "start": "expo start",
    "test": "jest"
  },
  "dependencies": {
    "expo": "58.0.0"
    %%placeholder-start%%... %%placeholder-end%%
  }
}

Platform-specific hook behavior

To run a script (or some part of a script) only for Android or iOS builds, you can fork the behavior depending on the platform within the script. See the following common examples to do this through a shell script or a Node script.

Examples

package.json and shell script

{
  "name": "my-app",
  "scripts": {
    "eas-build-pre-install": "./pre-install",
    "start": "expo start"
    %%placeholder-start%%... %%placeholder-end%%
  },
  "dependencies": {
    %%placeholder-start%%... %%placeholder-end%%
  }
}

#!/bin/bash

# This is a file called "pre-install" in the root of the project

if [[ "$EAS_BUILD_PLATFORM" == "android" ]]; then
  echo "Run commands for Android builds here"
elif [[ "$EAS_BUILD_PLATFORM" == "ios" ]]; then
  echo "Run commands for iOS builds here"
fi

Because the hook calls ./pre-install directly, the pre-install file needs execute permission. Set the permission and commit the change, so that Git records it with the file:

Without execute permission, the hook fails with a Permission denied error. Another option is to call the script with bash, as in "eas-build-pre-install": "bash ./pre-install". Then the file does not need execute permission.

if [[ "$EAS_BUILD_PLATFORM" == "ios" ]]; then
  if brew list git-lfs > /dev/null 2>&1; then
    echo "=====> git-lfs is already installed."
  else
    echo "=====> Installing git-lfs"
    HOMEBREW_NO_AUTO_UPDATE=1 brew install git-lfs
    git lfs install
  fi
fi

package.json and Node script

{
  "name": "my-app",
  "scripts": {
    "eas-build-pre-install": "node pre-install.js",
    "start": "expo start"
    // ...
  },
  "dependencies": {
    // ...
  }
}

// Create a file called "pre-install.js" at the root of the project

if (process.env.EAS_BUILD_PLATFORM === 'android') {
  console.log('Run commands for Android builds here');
} else if (process.env.EAS_BUILD_PLATFORM === 'ios') {
  console.log('Run commands for iOS builds here');
}