# Transform

Declares transforms by name for use in policies, views, cursors, etc.

For backwards compatibility (cortex < 2.13.0), any transform not assigned a name takes on the `export` property of the library in which it is defined.

A transform can extend `require('runtime.transform').Transform` or not. If it does, the transform can tweak the default limits for the `each()` cycle in the constructor.

See the section on scripting transforms for more examples.

```javascript
const { transform } = require('decorators'),
      { Transform } = require('runtime.transform')

@transform('c_random_transform', { environment: 'production', weight: 1 })
class AddRandomTransform extends Transform {

    constructor(transformOptions, runtimeOptions) {
      super({
        opsThreshold: 0.65, // defaults to .8. exits the each() cycle after 65% ops usage.
        msThreshold: 0.65,  // defaults to .8. exits the each() cycle after 65% time usage.
        minMs: 1000, // defaults to null. exits the each() cycle when less that minMs time is left.
        minOps: 100000 // defaults to null. exits the each() cycle when less that minOps ops are left.
      })
    }

    each( object ) {
        return { ...object, random: Math.random() }
    }

    // a particularly long running after script could cause the transform to
    // fail so the defaults have been tweaked.
    after() {

    }

}
```

## @transform(name, options) / @transform(options)

*Arguments*

* `options` { Object } Options object
  * `name` { String } The custom (`c_`) name of the transform. Used to register and override existing transforms.
  * `environment` { String = *"\*"* } Limits registering to an environment. Possible values (\*, production, development).
  * `weight` { Number = *0* } The transform weight.&#x20;

## Constructor Options

* `transformOptions` { Object } Unused
* `runtimeOptions` { Object } Options passed to the transform class constructor
  * `runtime` { Object }
    * `name` { String }
    * `environment` { String = *"\*"* }
    * `weight` { Number = *0* }
    * `metadata` { Object }
      * `resource` { String }
      * `className` { String }
      * `methodName` { String }
      * `static` { Boolean }
      * `loc` { Object }
        * `line` { String }
        * `column` { String }