No intellisense for Javascript projects

[AndrewRayCode]

For example without even having to analyze user Javascript classes, basic intellisense is missing:

I type test., nothing happens so I type Ctrl-Space and after 1-2 seconds(!) an empty menu comes up.

Function arguments aren't suggested:

My jsconfig.json:

{
    "compilerOptions": {
        "target": "ES6",
        "module": "commonjs"
    },
    "exclude": [
        "node_modules"
    ]
}

[jrieken]

duplicate of #2054