anchor.diff:  * Phases: `build`
   * Value: false
   
  -### <a id="environment-variable-npm-config-loglevel"></a> NPM\_CONFIG\_LOGLEVEL
  +### <a id="environment-variable-npm-config-loglevel"></a> NPM_CONFIG_LOGLEVEL
   
   The `NPM_CONFIG_LOGLEVEL` environment variable adjusts the level of logging NPM uses.
   
  
positive.code: 
  ### <a id="environment-variable-node-env"></a> NODE_ENV
  
  The `NODE_ENV` environment variable specifies which environment the application is running in.
  
  * Set by: `node-engine-cnb`
  * Phases: `build`
  
negative.code: 
  #### <a id="layer-reuse-strategy"></a> Determining Layer Reuse
  
  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
  
  