Hooks

Introduction

Cordova Hooks represent special scripts which could be added by application and plugin developers or even by your own build system to customize cordova commands.

Cordova hooks allow you to perform special activities around cordova commands. For example, you may have a custom tool that checks for code formatting in your javascript file. And, you would like to run this tool before every build. In such a case, you could use a 'before_build' hook and instruct the cordova run time to run the custom tool to be invoked before every build.

Hooks might be related to your application activities such as before_build, after_build, etc. Or, they might be related to the plugins of your application. For example, hooks such as before_plugin_add, after_plugin_add, etc applies to plugin related activities. These hooks can be associated with all plugins within your application or be specific to only one plugin.

Cordova supports the following hook types:

Ways to define hooks

Config.xml

Hooks could be defined in project's config.xml using <hook> elements, for example:

<hook type="before_build" src="scripts/appBeforeBuild.bat" />
<hook type="before_build" src="scripts/appBeforeBuild.js" />
<hook type="before_plugin_install" src="scripts/appBeforePluginInstall.js" />

<platform name="android">
    <hook type="before_build" src="scripts/android/appAndroidBeforeBuild.bat" />
    <hook type="before_build" src="scripts/android/appAndroidBeforeBuild.js" />
    <hook type="before_plugin_install" src="scripts/android/appAndroidBeforePluginInstall.js" />
    ...
</platform>

<platform name="windows">
    <hook type="before_build" src="scripts/windows/appWinBeforeBuild.bat" />
    <hook type="before_build" src="scripts/windows/appWinBeforeBuild.js" />
    <hook type="before_plugin_install" src="scripts/windows/appWinBeforePluginInstall.js" />
    ...
</platform>

Plugin hooks (plugin.xml)

As a plugin developer you can define hook scripts using <hook> elements in a plugin.xml like that:

<hook type="before_plugin_install" src="scripts/beforeInstall.js" />
<hook type="after_build" src="scripts/afterBuild.js" />

<platform name="android">
    <hook type="before_plugin_install" src="scripts/androidBeforeInstall.js" />
    <hook type="before_build" src="scripts/androidBeforeBuild.js" />
    ...
</platform>

before_plugin_install, after_plugin_install, before_plugin_uninstall plugin hooks will be fired exclusively for the plugin being installed/uninstalled.

Order of Hooks execution

Based on Hooks Definition

Hook scripts for one given hook run serially in the order of appearance in their file with application hooks from config.xml running before plugin hooks from plugins/.../plugin.xml.

Based on the Internal order of execution

The internal order of execution of hooks is fixed.

Example 1 (cordova platform add)

If there are hooks associated with before_platform_add, after_platform_add, before_prepare, after_prepare, before_plugin_install and after_plugin_install (and assuming you have one plugin installed on your project), adding a new platform will execute the hooks in the following order:

before_platform_add
    before_prepare
    after_prepare
    before_plugin_install
    after_plugin_install
after_platform_add

Example 2 (cordova build)

If there are hooks associated with before_prepare, after_prepare, before_compile, after_compile, before_build and after_build - running a build command will execute the hooks in the following order:

before_build
    before_prepare
    after_prepare
    before_compile
    after_compile
after_build

Script Interface

Javascript

If you are writing hooks using Node.js you should use the following module definition:

module.exports = function(context) {
    ...
}

Here is an example that showcases the contents of the context object:

{
  // The type of hook being run
  hook: 'before_plugin_install',

  // Absolute path to the hook script that is currently executing
  scriptLocation: '/foo/scripts/appBeforePluginInstall.js',

  // The CLI command that lead to this hook being executed
  cmdLine: 'cordova plugin add plugin-withhooks',

  // The options associated with the current operation.
  // WARNING: The contents of this object vary among the different
  // operations and are currently not documented anywhere.
  opts: {
    projectRoot: '/foo',

    cordova: {
      platforms: ['android'],
      plugins: ['plugin-withhooks'],
      version: '0.21.7-dev'
    },

    // Information about the plugin currently operated on.
    // This object will only be passed to plugin hooks scripts.
    plugin: {
      id: 'plugin-withhooks',
      pluginInfo: { /* ... */ },
      platform: 'android',
      dir: '/foo/plugins/plugin-withhooks'
    }
  },

  // A reference to Cordova's API
  cordova: { /* ... */ }
}

You can also require additional Cordova modules in your script using context.requireCordovaModule in the following way:

const cordovaCommon = context.requireCordovaModule('cordova-common');

You can make your scripts asynchronous using Promises. Here is an example that just waits for a second and then prints the amount of milliseconds spent waiting:

module.exports = context => {
    return new Promise(resolve => {
        const start = Date.now();
        setTimeout(() => resolve(Date.now() - start), 1000);
    }).then(msWaited => {
        console.log(`${context.scriptLocation} waited ${msWaited} ms`);
    });
};

Non-javascript

Non-javascript scripts are run via Node child_process spawn from the project's root directory and have the root directory passed as the first argument. All other options are passed to the script using environment variables:

If a script returns a non-zero exit code, then the parent cordova command will be aborted.

Note: we highly recommend writing your hooks using Node.js so that they are cross-platform, see Javascript section above.

Windows Quirks

If you are working on Windows, and your hook scripts aren't *.bat files, Cordova CLI will expect a shebang line as the first line of the script. This way it knows the interpreter it needs to use to launch the script. A shebang line for a Python script could look like this:

#!/usr/bin/env python

Sample Usage

This sample demonstrates Cordova hooks usage to trace to the console output the size of generated .apk file for Android platform.

Create blank Cordova app and add the following definition to config.xml to tell Cordova to run afterBuild.js script after each platform build.

<hook type="after_build" src="scripts/afterBuild.js" />

Create scripts/afterBuild.js file and add the following implementation. We use async version of fs.stat method to demonstrate how async functions can be used in hooks.

const fs = require('fs');
const util = require('util');
const stat = util.promisify(fs.stat);

module.exports = function(ctx) {
    // Make sure android platform is part of build
    if (!ctx.opts.platforms.includes('android')) return;

    const platformRoot = path.join(ctx.opts.projectRoot, 'platforms/android');
    const apkFileLocation = path.join(platformRoot, 'build/outputs/apk/android-debug.apk');

    return stat(apkFileLocation).then(stats => {
      console.log(`Size of ${apkFileLocation} is ${stats.size} bytes`);
    });
};

Parameter ctx in example above is passed by Cordova and represents execution context such as script full path, target platform, command-line arguments, etc and also exposes additional helper functionality. See Script Interface section above for more details.

You can now add android platform and execute build.

cordova platform add android
..
cordova build
..
Size of path\to\app\platforms\android\build\outputs\apk\android-debug.apk is 1821193 bytes

More good usage examples could be found in Three Hooks Your Cordova Phone Gap Project needs