If the below line is used in the javascript code:const express = require(express);
then autocomplete / intellisense will not work. It will not display the relevant methods as shown in the image below.

This is the correct code to use:const express = require("express");
The quotation marks make the difference and the following image shows the listen() method:

To enable intellisense for express.js see the extension to enable node.js at https://askmeaboutlinux.com/2023/01/23/moving-from-atom-to-visual-studio-code-and-its-extensions-on-linux/