Use of const in strict mode : Azure Web App

Question

Application has thrown an uncaught exception and is terminated: SyntaxError: Use of const in strict mode.
    at Module._compile (module.js:434:25)
    at Object..js (module.js:464:10)
    at Module.load (module.js:353:31)
    at Function._load (module.js:311:12)
    at Module.require (module.js:359:17)
    at require (module.js:375:17)
    at Object.<anonymous> (D:\home\site\wwwroot\node_modules\mongoose\index.js:7:18)
    at Module._compile (module.js:446:26)
    at Object..js (module.js:464:10)
    at Module.load (module.js:353:31)

Error is thrown everytime Azure Web App project is made and an Express App is published. I tried with Azure Express as well as Blank nodeJs App to do it

Answer 1

Looks like it's caused by an invalid node version on Azure. Go to Azure portal, your Web App - Application settings, check WEBSITE_NODE_DEFAULT_VERSION .

Once we specify a version not available on Azure, a quite old version 0.10.40 is in use, where const is not enabled by default so that we met SyntaxError: Use of const in strict mode . See related thread for more details.

We can use 10.6.0, 8.11.1, etc. Go to https://<yourwebappname>.scm.azurewebsites.net/api/diagnostics/runtime to see all versions available.

Caveat by Clinkz

In some cases, the above solution may not work. This may be because your project includes the file iisnode.yml . If this file exists, it overrides application settings environment variable. The content of this file should be as follows :

nodeProcessCommandLine: "%SystemDrive%\Program Files (x86)\nodejs\0.10.4\node.exe"

The node version specified here takes precendence. To fix it, simply update the version, like so and deploy:

nodeProcessCommandLine: "%SystemDrive%\Program Files (x86)\nodejs\8.9.4\node.exe"

Refer to this .

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To conclude , the priority: iisnode.yml > package.json(engine)> Application settings. Application setting is recommended as it's easy to check and modify on portal.