anchor.diff:  
   #### <a id="layer-reuse-strategy"></a> Determining Layer Reuse
   
  -In order to improve build times for applications, the NPM CNB has a strategy for reusing the build results from previous builds. When it can be determined that a portion of the build process can be reused from a previous build, the CNB will opt to use the previous result. Each installation process has a different strategy for determining whether a previous build result can be used.
  -
  -For `npm install`, previous build results are never reused.
  -
  -For `npm rebuild`, previous build results are reused if the `node_modules` directory included in the application source code has not changed since the prior build.
  -
  -For `npm ci`, previous build results are reused if the `package-lock.json` file included in the application source code has not changed since the prior build.
  +To improve build times for apps, the NPM CNB has a method for reusing the build results from previous builds. When the CNB determines that a portion of the build process can be reused from a previous build, the CNB uses the previous result. Each installation process uses a different method for determining whether the CNB can reuse a previous build result.
  +
  +For `npm install`, the CNB never reuses previous build results.
  +
  +For `npm rebuild`, the CNB reuses previous build results if the `node_modules` directory included in the app source code has not changed since the prior build.
  +
  +For `npm ci`, the CNB reuses previous build results if the `package-lock.json` file included in the app source code has not changed since the prior build.
  +
   
   ## <a id="package-management-with-yarn"></a> Package Management with Yarn
   
  
positive.code: * Phases: `build`
  * Value: "error"
  
  ### <a id="environment-variable-npm-config-production"></a> NPM\_CONFIG\_PRODUCTION
  
  The `NPM_CONFIG_PRODUCTION` environment variable installs only production dependencies if NPM install is used.
  
  
negative.code: 
  ### <a id="environment-variable-node-env"></a> NODE_ENV
  
  The `NODE_ENV` environment variable specifies the environment in which the app runs.
  
  * Set by: `node-engine-cnb`
  * Phases: `build`
  