I have not yet migrated my Ionic3 app to Ionic4, and continued using the last Ionic3 version that I had installed (3.20) before Ionic4 came out. I assumed that in order to use Ionic4, the code itself would have to be compatible with all the changes that came with Ionic4 - the new project structure/folders, installing Angular 6 and up, changing component and function names and so on.
After recently installing the latest Ionic4 version by accident via npm install -g ionic, I did a clean npm install on the Ionic3 project without changing anything in the package.json, and after ionic serve the Ionic3 app seems to run without any problems.
I did not see anything official from Ionic regarding this issue or backwards compatibility support - Is it OK to continue with Ionic3 code and an Ionic4 version installed? Or is there some other reason?
package.json
"scripts": {
"clean": "ionic-app-scripts clean",
"build": "ionic-app-scripts build",
"ionic:build": "ionic-app-scripts build",
"ionic:serve": "ionic-app-scripts serve"
},
"dependencies": {
"@angular/animations": "5.0.3",
"@angular/common": "5.0.3",
"@angular/compiler": "5.0.3",
"@angular/compiler-cli": "5.0.3",
"@angular/core": "5.0.3",
"@angular/forms": "5.0.3",
"@angular/http": "5.0.3",
"@angular/platform-browser": "5.0.3",
"@angular/platform-browser-dynamic": "5.0.3",
"@angular/platform-server": "5.0.3",
"angularfire2": "4.0.0-rc.1",
"es6-promise-plugin": "^4.2.2",
"firebase": "4.4.0",
"ionic-angular": "^3.9.3",
"moment": "^2.22.2",
"promise-polyfill": "6.1.0",
"rxjs": "5.5.2",
"sw-toolbox": "^3.6.0",
"zone.js": "0.8.18"
},
"devDependencies": {
"@ionic/app-scripts": "^3.2.3",
"typescript": "2.4.2"
}
}
And the Ionic version
