https://github.com/jpommerening/crossgrade

An abstract migration framework for use in versioned APIs and databases
https://github.com/jpommerening/crossgrade

Last synced: 24 days ago
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An abstract migration framework for use in versioned APIs and databases

• Host: GitHub
• URL: https://github.com/jpommerening/crossgrade
• Owner: jpommerening
• License: mit
• Created: 2015-06-26T09:07:38.000Z (over 9 years ago)
• Default Branch: master
• Last Pushed: 2015-07-03T08:54:48.000Z (over 9 years ago)
• Last Synced: 2024-10-13T05:01:39.885Z (about 1 month ago)
• Language: JavaScript
• Size: 539 KB
• Stars: 0
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# ![crossgrade](media/logo.png)

An abstract migration framework for use in versioned APIs and databases.

```js

var xg = require('crossgrade');

var migration = xg([

  // Migrations are function that are applied to

  // get from one semantic version to another

  { from: '0.1.0', to: '0.2.0', fn: migrationFunction },

  // You can also use semantic version ranges if your function

  // can handle multiple versions

  { from: '~0.2.0', to: '~0.3.0', fn: migrationFunction },

  // Asynchronous rules receive a callback function as the last parameter

  { from: '0.3.0', to: '0.4.3', async: true, fn: asyncMigrationFunction },

  // If you want to support conversion in both directions,

  // you can supply an "up" and a "down" function

  { from: '~0.4.0', to: '1.0.0', up: upgradeFunction, down: downgradeFunction },

  // Also, sub-migrations may be embedded as Crossgrade instances

  { from: '^1.0.0', to: '2.0.0', fn: xg(require('./1.0-to-2.0-migration-steps')) },

  // Of course, you are free to split your migrations into multiple files

  require( './3.0-migration-module' )

]);

migration.from('0.1.0')

         .to('1.0.0')

         .apply(instanceToUpgrade,

                ['args', 'passed', 'to', 'migration', 'methods']);

// Migration functions receive the versions as semantic version objects,

// the arguments that are passed in and the instance they are applied on

function migrationFunction(from, to, args, passed, to, migration, methods) {

  from instanceof semver.SemVer === true;

  to instanceof semver.SemVer === true;

  doSomethingWith(this);

}

```

## Use case: REST API versioning

Assuming somewhere in your middleware stack you set `req.apiVersion`, for example by

inspecting the _Accept-Type_ header and there is `res.body` which will be encoded by

another middleware:

```js

var semver = require('semver');

var xg = require('crossgrade');

var migration = xg(migrations);

var schemaVersion = semver('1.0.0');

app.use(function (req, res, next) {

  var acceptVersion = semver.Range(req.apiVersion);

  if (acceptVersion.test(schemaVersion))

    return next();

  migration.from(schemaVersion).to(acceptVersion).apply(res.body, next);

});

```