How to indicate that a variable is an Express object using Javascript Docs?

Question

I’m using the consign to automatically include routes in an application built with Express. In a given file I have the route:

module.exports = app => {
    app.post('/users', (req, res) => {
        //...
    })
}

But this approach, at least for me, resulted in the loss of Javascript Intellisense autocomplete in VS Code.

It would be possible using Javascript documentation tags to instruct the IDE/Editor, in this case VS Code to understand that app is an object of the Express, leading the same to "reactivate" the Intellisense? How could this be done?

Answer 1

It is possible, if you create an annotation with the type of this variable.

Intellisense accepts Jsdoc annotations to indicate the type of the variable with the following syntax:

/** 
 * @param { string } arg1
 * @param { boolean } arg2
 */
function minhaFuncao(arg1, arg2) {

}

From this model, you can check in the module index.d.ts Express, that kind of his app, is Express, soon you can create an indication for your type app with:

/** @param { import('express').Express } app */
module.exports = app => {
  app.post('/users', (req, res) => {
    // ...
  })
}

From there, Intellisense knows the type of app, and then also recognizes the signature of the method post, also recognizing the type of arguments req, res and next.