8. Moving to Express 4

Moving to Express 4

Overview

Express 4 is a breaking change from Express 3. That means an existing Express 3 app will not work if you update the Express version in its dependencies.

This article covers:

• Changes in Express 4.
• An example of migrating an Express 3 app to Express 4.
• Upgrading to the Express 4 app generator.

Changes in Express 4

There are several significant changes in Express 4:

• Changes to Express core and middleware system. The dependencies on Connect and built-in middleware were removed, so you must add middleware yourself.
• Changes to the routing system.
• Various other changes.

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