Implicit VSCode Intellisense no longer work after renaming the JS file

Earlier, I have two JS files:

1. old-file.js
2. new-file.js

I later noticed that my app.js‘ intellisense was always referring to the old-file.js but not the new-file.js, so I deleted the old-file.js (as though I’ve renamed the old file). But now, when working on my app.js, the intellisense has gone missing, which means VSCode does not automatically make use of the definitions in the new-file.js, which has the same and also additional object declarations.

I tried looking for my Typescript and JavaScript Language Features built-in extension but can’t find it in my VSCode. I also restarted my VSCode many times but still not working. My jsconfig.json looks fine in the project root folder as shown below:

{
    "compilerOptions": {
        "module": "commonjs",
        "target": "es2016",
        "jsx": "preserve"
    },
    "exclude": [
        "node_modules",
        "**/node_modules/*"
    ],
    "typeAcquisition": {
        "include": [
            "jquery",
            "angular"
        ]
    }
}

Note that I was talking about the “implicit intellisense” of VSCode across external files, no import statements, nothing. Also note that my app.js and new-file.js will always be merged as app.min.js by terser at the later stage. Does anyone know what happen to my situation and how can I restore the intellisense of my new-file.js and put it back to work like the old one? Many thanks!