Learn Android, Babel and Chrome

Optional chaining ?. in javascript is a new feature introduced in ES2020. Optional chaining changes the way properties are accessed from deeply nested objects. It fixes the problem of having to do multiple null checks when accessing long chain of object properties in javascript.

JavaScript® (often shortened to JS) is a lightweight, interpreted, object-oriented language with first-class functions, most known as the scripting language for Web pages, but used in many non-browser environments as well such as node.js or Apache CouchDB. It is a prototype-based, multi-paradigm scripting language that is dynamic, and supports object-oriented, imperative, and functional programming styles.

javascript

Optional Chaining

Chrome DevTools are incredibly useful for a frontend developer, sometimes we spend more time using them than our text editor of choice.

That's why it's so important to understand this tool better - those quick lessons will teach you things that will help you to become a more effective developer.

You will learn how to:

- **Use (experimental) CSS Overview to learn all about CSS used on a page in a minute**
- **Style console.log messages with CSS** - a _crucial_ skill for any senior developer (j/k)
- **Debug your code (on production and local environment) with logpoints**
- **Run a Lighthouse audit of your site**
- **Choose accessible colors for your website that have an AAA contrast ratio rating**
- **Force a DOM element state in Chrome DevTools**
- **Use Console utilities to make debugging easier**
- **Copy a network request as fetch or cURL with Chrome DevTools**

Have fun!

The Chrome Developer Tools (DevTools for short), are a set of web authoring and debugging tools built into Google Chrome.

chrome-devtools

Chrome DevTools tips & tricks

In this course we’ll take a deep look at the Elements panel in the chrome devtools. We’ll step through each button and tab on this panel and discuss how to use them to interact with your web application as it runs.

Debug the DOM in Chrome with the Devtools Elements Panel

This course examines the Sources panel in the Chrome DevTools, which allows you to see what files are responsible for the various things on the screen. Bundled into this panel, though, is the single most useful tool for any JavaScript developer - the JavaScript Debugger. We’ll use the Debugger to inspect JavaScript as it runs, allowing you to watch (and even interact with) the state of your application as it runs in ways that’ll blow your mind if you’ve mostly used console.log to debug your applications to this point. 

Debug JavaScript in Chrome with DevTool Sources

This course will examine the Network panel in Chrome DevTools. We’ll step through the request log, examining the various properties exposed. We’ll talk about timing, filtering, throttling and generally using the network panel to better understand the ways in which our applications exist within a connected context.

Debug HTTP with Chrome DevTools Network Panel

Open source framework for building truly native mobile apps with Angular, TypeScript or JavaScript.

nativescript

We will learn how to add an Android library to our project and translate it’s Java api to NativeScript. For this lesson, we will look at [Filestack’s Android SDK](https://github.com/filestack/filepicker-android) built with Gradle. Specifically, we will cover how to immediately start working with the library even when a [NativeScript](/q/nativescript) plugin does not exist for it.

Use an Android library in NativeScript for Angular using Java apis

Java has been around a long time and when it comes to Android, you will encounter some structures that may throw you for a loop on how to code against with NativeScript. Let’s examine a few common Java/Android api constructs you may encounter and how to translate them to NativeScript. Learn how to get references to local files in your app using the ‘file-system’ module as well as how to take advantage of NativeScript’s Observable class to send notification events from one class to another. Lastly, look at considerations with Angular’s NgZone when handling your native libraries data events to update component view bindings.

Translate common Java/Android APIs into NativeScript for Angular Android apps

One of the exciting benefits you have with NativeScript is the ability to write native code (Java and Objective C) directly in JavaScript/TypeScript allowing you to create a consistent high level api over top of both underlying iOS Objective C/Swift and Android Java apis. In this lesson, we will look at how to design a consistent api that taps into the appropriate native api’s on the target platforms using underlying native libraries.

Develop a consistent plugin api across your Android and iOS NativeScript app

To prepare your development environment to code against native apis such as Objective C, Swift and Java, let's learn how to [install tns-platform-declarations](https://www.npmjs.com/package/tns-platform-declarations) to provide rich intellisense support for all the native iOS and Android api’s. This lesson will cover how to modify your tsconfig.json and references.d.ts properly to ensure working with native api’s is smooth and as helpful as possible.

Prepare for native iOS and Android api intellisense with NativeScript

 AJAX allows us to send requests to the server from our javascript applications, rather than allowing the browser to directly request declaratively specified resources. Under the hood, though, AJAX requests are still just HTTP requests - and that means we can use the Network Panel in Chrome’s DevTools to inspect our AJAX operations!


Examine AJAX Requests with Chrome Devtools

To understand the Network DevTool, you have to understand what HTTP is and how it works. Let’s use the Network DevTool to inspect an HTTP request and its corresponding response so that we can understand what the browser is doing.

Analyze HTTP Requests and Responses with Chrome Devtools

Most of today’s websites use optimized, compiled, minified and obfuscated javascript and CSS. Examining this stuff here has some severely limited utility, which is why when developing we rely on sourcemaps. We’ll set up a webpack workflow that uses sourcemaps to show you how they can help your debugging!

Unbundle your JavaScript with Source Maps in Chrome DevTools

Building a custom NativeScript XML view component for Android is uniquely different than it’s iOS counterpart because of the Android Context which must be considered. Let’s look at how to properly build a custom view component based on an underlying native view widget. We will also look at what happens when our include.gradle file is not setup properly including handling problems with minimum sdk targets with plugins. Specifically, we will implement this Android widget representing the [Google I/O 2016 clock](https://github.com/lypeer/GoogleClock). Learn how to create a custom AndroidManifest.xml inside your plugin to merge with your app's manifest to override certain characteristics. Read detailed documentation about the [Android app manifest file](https://developer.android.com/guide/topics/manifest/manifest-intro.html).

Build a custom NativeScript view component for Android

Learn to use the Style panel within the Element Inspector to examine and tweak the CSS rules applied to your application as it runs. 

Chrome Devtools: Elements - Debug with Style!

The Element Inspector in Chrome DevTools offers powerful integration with the console - learn how to programmatically navigate your selected element, how to search through the history and use CSS selectors to control what you're looking at and how to quickly and easily listen for events as you debug your application.

Chrome Devtools: Elements - Console Integration

Use the Event Listeners tab within the Elements panel to list all DOM Event listeners. This is useful to understand how and why your site is reacting to various forms of input.

Understand the Event Listeners Panel

The Elements panel includes a tool to show you how your site will look across a variety of devices. This can be tremendously helpful when troubleshooting layout issues on specific hardware that you don’t have access to, as well as general-purpose response design. You can mock different screen resolutions and behaviors to help put you into your users’ shoes.

Use the Device Toolbar to Emulate Different Screens

There are a variety of ways to trigger the javascript debugger. Use the elements panel to set breakpoints on DOM elements so that you can hit the debugger whenever an element’s children or attributes change, or when it’s removed.

Use DOM Break Points

Using the Snippets tab in the source devtool you can define and run arbitrary pieces of code in your browser against whatever website you’re looking at. This is a great way to store commonly used pieces of code that you rely on for debugging or customization.

Use Snippets to Store Behaviors in Chrome DevTools

There are a variety of ways to trigger the debugger in Chrome's DevTools. You can set breakpoints on line numbers, break on XHR requests or DOM changes, break on specific events or even manually break by using the special `debugger` keyword in your code.

Set Breakpoints for the Chrome Debugger

Use the Chrome Debugger to pause execution of your application as it runs to see what’s happening in slow-motion. The debugger is an advanced tool that allows you to examine every change that happens in your application so that you can understand how and why your application state evolves over time.

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