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How does it work?

Explanation of Mosaic's work mechanics

This article mostly is for the contributors who are willing to enhance the Mosaic's core package's (@tilework/mosaic) behaviour with additional functionality.

Read the code for more information, or feel free to use our Github Discussionsarrow-up-right to ask us for specifics!

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Features

middleware - a method to attach a namespace to a piece of functionality and ensure the plugins work for that namespace

Extensible - a method to ensure proper context during the construction of the given class. Important for interception of class properties being declared with class property syntaxarrow-up-right during their initialisation in the constructor

setPlugins - a method that accepts an array of modules (which are .plugin.js files), sets the internal property and exposes it to the window object.

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How ?

The middleware function wraps functionality (further - "middlewarable") into a Proxyarrow-up-right, and assigns a namespace to it.

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If the middlewarable is a function

When it is called, the following happens:

  1. The plugins are being extracted from the lib/plugins/plugin-storage

  2. These plugins are wrapped around the initial function, thus generating a new function

  3. This function is called on the original arguments

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If the middlewarable is a class

During the new call, the following happens:

  1. Extensible ensures that the instance is a Proxyarrow-up-right from the very beginning, this Proxy intercepts all members' accesses and applies plugins on the fly

  2. All of the member-property plugins are applied to it, replacing the original properties with the ones the plugins result into.

Afterwards, when the object is used, the following happens:

  1. When calling any member of the instance, the plugin storage is scanned for the plugins for that member, and if any are found - they are applied to the callable member before executing it

Also, the following is applied to the class itself

  1. The class itself is a Proxyarrow-up-right, to ensure that calls to static properties are handled as member properties - by immediate replacement. It is a proxy only when is accessed from within its instance, otherwise it is not a proxy.

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If the middlewarable is a primitive

This is not supported

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