Develop Reference

VS Code intellisense for Javascript built-in function

In Javascript for some methods, I don't see the suggestions. For example indexOf, charCodeAt and so on. Is it possible to activate suggestions for these built-in Javascript keywords?

I think you should leverage VS Code ability to work with JSDoc.
As you can see without JSDoc, VS Code can't infer that bar is a string. After documenting the parameter properly, it is able to make some meaningful suggestions:

How to get jsdoc generation for parms of class methods that use arrow functions?

I'm a student who's capstone project/work intergrated learning is about to end. I'm working on producing technical documentation to hand off to the next team that will continue on with this work, but I've hit a snag.
My class methods that use arrow functions aren't generating params documentation when I create documentation using the jsdoc tool.
i.e.:
becomes
The documentation works as intended in visual studio code/intellisense:
I've been googling around to try and figure out what the problem was, but I failed to find anything.
I mean, my research yielded:
Outdated way to make vscode play nice with arrow function
syntax: (https://github.com/Microsoft/vscode/issues/36283) (https://github.com/Microsoft/vscode/issues/22264) ((This one is the actual issue where the support was added) https://github.com/microsoft/TypeScript/issues/14134)
Outdated info on the jsdoc support for this feature:
https://github.com/jsdoc/jsdoc/issues/1310
etc., etc., again, nothing useful.
Of note is that I'm using the jsdoc-export-default-interop plugin so that jsdoc will actually generate things for export default [CLASS OR FUNCTION].

I've found a solution that fits my requirements
However, while it is good enough for my purposes, I'm not entirely sure it's acurate and would be happy to hear critisims, other people's viewpoints and solutions. I'll explain the concerns I have at the end.
The problem: It looks like jsdoc cannot automatically detect if a member assignment is a function when parsing.
I have no idea why VSCode is able to detect it automatically, but it appears the JSDoc tool cannot. Here it is stated in the official documentation
Link to documentation: (https://jsdoc.app/tags-function.html)
The solution: Document the member with the #function tag (or an alias like #method).
By documenting the class member with the #function tag like so:
I am able to get the arrow function to generate as a class method, and get params documentation:
My concerns
Well the biggest concern/annoyance is now I need to go through all the source code and add a bunch of #function tags. Ah whelp.
Other concerns are that I may have misunderstood the problem/I'm not quite sure if this is best practice.
And I'm not too certain if this documentation is accurate in terms of if there is actually a tangible difference between a class member arrow function and a class method that I need to capture in the API documentation.
Anyway, I think this will be what I go with, but I'll be monitoring this answer to read any input/feedback :)

Safe navigation operator in Reactjs using JSX

I am using Reactjs via JSX. Is there any safe navigation operator to use in this method? I tried using question mark operator like "foo?.bar" but I got syntax error.

The safe navigation operator (aka. Elvis operator) is a proposal in draft status with TC39, so no. Not yet anyway (as of this writing).
But this ugly syntax will get you there without a library. Instead of ...
foo?.bar
... use this ...
(foo||{}).bar||{}
It's hard to read but it works and it isn't dependent on a library.
UPDATE: The proposal has reached stage 4, so it will be part of ES2020.

You can use from get method in lodash library, like this:
import { get } from 'lodash';
get(foo, 'bar1.bar2.bar3.bar4');

Now, there is a babel plugin called #babel/plugin-proposal-optional-chaining that solves this problem.

How to get rid of editor’s error for object.key

I have the following code that basically gets some JSON data, looks for the keys with "servergenre", and saves the results in an array.
This is a follow up of this question.
let result = [];
Object.keys(data).forEach( key => {
if(/servergenre/.test(key)){
result.push(data[key])
}
});
Even though the code is working correctly, in some editors it raises syntactic errors:
"key": unsolvable variable or type key
"=>": expression expected
"if( / server...": formal parameter name expected
")){": , expected
"});": statement expected
Here is an image to show you where the errors are:
As I said the code is working fine, I just need it to be fixed or another approach to get rid of the errors.
Furthermore, many compressors and minifiers do not support this bit of code. So I can’t minify it.
Thanks in advance.

ES2015, formerly known as ES6, is a more recent version of JavaScript, which introduces features such as the => syntax for functions you are using.
Not all features of ES2015 are fully supported in all browsers, so many people who use it pass it through a compiler (“transpiler”) first to convert it to ES5, which is supported by all browsers. Babel is one such transpiler. But if you are only targeting newer browsers, that would explain why the => syntax is working for you.
You just need to change your editor settings to understand that syntax. Exactly how you do that depends on what text editor you are using. It could be that your editor's built-in JavaScript mode doesn't know how to read ES2015 syntax, and you need to either upgrade your editor or install a third-party plugin that provides an updated error-checker. Or it could be that your editor supports both ES5 and ES2015, and it thinks you are trying to write your project only in ES5. In this case you just need to go to the settings and tell your editor that you mean for this project to use ES2015 (or ES2016, which is currently the most recent version).

Fat arrows are ES6 syntax. If that causes trouble, just write good old ES5 :
let result = [];
Object.keys(data).forEach( function(key) {
if(/servergenre/.test(key)){
result.push(data[key])
}
});

JSON.stringify() is this object and function standard to javascript?

I have never seen it before until today and it seems to just work without including any .js or framework. is this a standard object in javascript? if so where can I find the documentation for it and other uncommon Objects that are available in javascript

Looks like you need to learn about MDN
https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/JSON/stringify

It's part of the ES5 specification. See http://es5.github.io/ for the whole annotated spec and for this function specifically see http://es5.github.io/#x15.12.3
See also http://caniuse.com/#search=json for a browser support matrix.

Yes it is. It's a standard object, in common use and works in all current browser versions. Documentation here.
The only time you'll have a problem with it is in old IE versions; if you need to support them, you'll need to use a polyfill library like this one.