Hello, World! I've been importing node libraries ...

# javascript

[bod]

Hello, World!

I've been importing node libraries and using them successfully, but for this one (express) I'm trying to use and am hitting something I don't understand.

I've added this dependency:

implementation(npm("express", "4.17.3"))

And declared this external:

@file:JsModule("express")
@file:JsNonModule

package express

external fun express(): dynamic

But calling express() in my code gives me:

TypeError: express_0 is not a function

Any idea why it's named express_0 in the generated js? 🤔

[turansky]

@file:JsModule("express")
@file:JsNonModule

package express

@JsName("default")
external fun express(): dynamic

?

[ansman]

Try adding @JsName("express") to the external definition

[bod]

Thanks for the tips! Just tried (both "default" and "express") but am still getting the same error.

[turansky]

@JsModule("express")
external fun express(): dynamic

?

[bod]

@turansky @JsModule and @JsNonModule can't appear on here since the file is already marked by either @JsModule or @JsNonModule

[turansky]

Remove file annotation 🙂

[bod]

yes that works! 🎉 First, thanks! 🙏 Second, any idea why? Annotating the whole file worked with other libraries.

[turansky]

• Old JS module style in express
• Missed JsModule configuration

[bod]

Missed JsModule configuration

sorry, not sure what you mean by this one

[turansky]

Issue

[turansky]

Member annotation cover all cases in ScalaJS:

// old style
@JsImport(JsImport.Namespace)
external val express(): Express

// default import
@JsImport(JsImport.Default)
external val express(): Express

// named
@JsImport("express")
external val express(): Express

[turansky]

old style - your case

[bod]

I see. Thanks a lot! I admit I'm not 100% sure I understand JsModule vs JsNonModule (and the docs I found were a bit taciturn)

[turansky]

Screenshot 2022-04-21 at 21.12.22.png

[turansky]

@JsImport is more flexible, cover all cases and it’s synchronous with @JsExport

Also such scheme allows to declare extensions in the same file

[turansky]

Related example