build.gradle

apply plugin: 'com.android.library'

def safeExtGet(prop, fallback) {
    rootProject.ext.has(prop) ? rootProject.ext.get(prop) : fallback
}

android {
    compileSdkVersion safeExtGet('compileSdkVersion', 28)
    buildToolsVersion safeExtGet('buildToolsVersion', "28.0.0") 

    defaultConfig {
        minSdkVersion safeExtGet('minSdkVersion', 16)
        targetSdkVersion safeExtGet('targetSdkVersion', 28)
        versionCode 1
        versionName "0.0.1"
    }
}

dependencies {
    implementation "com.facebook.react:react-native:${safeExtGet('reactNativeVersion', '+')}"
    implementation "com.anjlab.android.iab.v3:library:${safeExtGet('anjlabIABVersion', '1.0.44')}"
}