In Node.js how to notice a missing function?

user_294884 0
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In some Node.js, I had

function examp() {
    ..
    blah = bestAvailableDelauneySlot()
    ..
}

However the function bestAvailableDelauneySlot did not exist at all.

(In my case I had foolishly forgotten to type the module, so, it should have been blah = triangles.bestAvailableDelauneySlot() ..)

Now, the code

  blah = bestAvailableDelauneySlot()

doesn't create any error AT ALL, until, for some reason examp is called at runtime. (Which only happens in obscure situations, once a week).

VSCode does not at all tell me there is no definition for bestAvailableDelauneySlot. "using strict" does not seem to help.

How the heck to safeguard against an undefined function name??

A simple typo

blah = triangles.bestAvailableDelauneySlozz()

and crash. Solution?

Perhaps ideally something that integrates w/ VSCode?

(BTW I generally use VSCode on a Mac ... perhaps that's the problem :O )

node.js undefined
2 Answers

The tool ESLint is the de facto standard to check for problems in JavaScript code.

In your specific case, the rule no-undef would report the undeclared function.

There's also an extension for Visual Studio Code with more than 12 million downloads:

ESLint for Visual Studio Code applied to the example

user_11780160

I want to provide two methods. I hope it could help you. More detail in Type checking JavaScrip.
Note: this is vscode.

First

You could simply add // @ts-check in the head of file to validate. Before you add // @ts-check, it doesn't tell you an error (bestAvailableDelauneySlot doesn't exist).

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Then you add // @ts-check, it will tell you it doesn't exist.

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Then you declare the function, the error is gone.

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If you make some typo, it will show error message.

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And it also work in module.exports and require. No // @ts-check.

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Add // @ts-check.

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Second

If you don't want to add //@ts-check by every file, you could create jsconfig.json in project root to enable whole files checking with adding checkJs in jsconfig.json. Its effect is same as adding //@ts-check in all files.

{
    "compilerOptions": {
        "checkJs": true
    },
    "exclude": ["node_modules", "**/node_modules/*"]
}
user_88715690
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