Single page apps in depth

A Book on single page apps development,what is it and how?


Why do we want to write single page apps? The main reason is that they allow us to offer a more-native-app-like experience to the user.

A modern web application architecture

Modern single page apps are generally structured as follows:

More specifically:

Write-only DOM. No state / data is read from the DOM. The application outputs HTML and operations on elements, but nothing is ever read from the DOM. Storing state in the DOM gets hard to manage very quickly: it is much better to have one place where the data lives and to render the UI from the data, particularly when the same data has to be shown in multiple places in the UI.

Models as the single source of truth. Instead of storing data in the DOM or in random objects, there is a set of in-memory models which represent all of the state/data in the application.

Views observe model changes. We want the views to reflect the content of the models. When multiple views depend on a single model (e.g. when a model changes, redraw these views), we don’t want to manually keep track of each dependent view. Instead of manually tracking things, there is a change event system through which views receive change notifications from models and handle redrawing themselves.

Decoupled modules that expose small external surfaces. Instead of making things global, we should try to create small subsystems that are not interdependent. Dependencies make code hard to set up for testing. Small external surfaces make refactoring internals easy, since most things can changes as long as the external interface remains the same.

Minimizing DOM dependent-code. Why? Any code that depends on the DOM needs to be tested for cross-browser compatibility. By writing code in a way that isolates those nasty parts, a much more limited surface area needs to be tested for cross-browser compatibility. Cross-browser incompatibilities are a lot more manageable this way. Incompatibilities are in the DOM implementations, not in the Javascript implementations, so it makes sense to minimize and isolate DOM -dependent code.


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