Develop Reference

Creating a circular slider in React Native

I am wanting to create a circular slider in React Native for a project of mine. Although I am not entirely sure on how to create one. Could someone help me out?
Here is a little sketchup of what I want it to look like:
I did some searching on the interwebs and found some posts about circular sliders in React Native. But these posts seem to be dated and the projects linked/provided in these posts would not work for me.
1. https://stackoverflow.com/questions/51058669/react-native-circular-slider
2. https://stackoverflow.com/questions/38253804/how-to-make-a-circular-slider-in-react-native
Note: I am fairly new to the world of React and React Native but do have decent experience with JavaScript. Right now I am still learning about React and React Native.

Your best best is probably svg via react-native-svg, since that will allow you to declaratively draw and animate arbitrary shapes without having to write platform-specific native code.
Note that setting up react-native-svg is slightly different if you are working with expo or have ejected, which may explain why some of those older examples you mentioned don't work (they pre-date expo).
Drawing with SVG is generally straight-forward, although you will need to use arc's in paths, which is about as awkward as SVG gets (but still not too bad).
The trickiest parts of a circular slider are capturing the touch input with PanResponder and converting coordinates between cartesian (x,y) coordinates of the touch input and polar (angle,distance) coordinate systems in order to know where to move the slider to.
In your case it looks like you want to lock the movement of the slider to specific increments around the clock so you'll also need to find the nearest increment to the polar-coord of the current touch, but that should be easy in polar coords - just find the increment with the closest angle to that of the touch.
Here is an Expo project that illustrates the slider part. It looks like this:

Based on the comments, if you are comfortable with the jQuery roundSlider then you can simply do the customization based on your need. Here I just make a mock up design, check the below demo:
DEMO
Also if you want this as an React component then you can make a simple wrapper like below, and can directly use in any React applications.
https://stackblitz.com/edit/react-jquery-round-slider
hope this will helps you, or will give you some idea to move in a direction.

Basic Javascript Drawing with User Editable Lines and Nodes

My research has found me powerful libraries like paper.js which are quick to show all the next-level awesome stuff they can do, but I'm not sure how (or if) I can accomplish a basic task:
I want to present a simple Stick Figure to my user:
o
\|/
/ \
Then let them grab the ends of the lines ("hands and feet"), and drag them into different positions, leaving the connecting nodes ("shoulders and hips") intact.
Simple.
In short, what is the simplest way to draw something with lines and nodes that users can manipulate.
Requirements:
Some line lengths are fixed, others can be lengthened.
Some nodes are fixed, others can be moved.
I need to at least display the angles of the lines, but ideally can modify those angles (via text input).
I feel like this shouldn't be this hard, but as I said, most libraries skip the basics and go straight to their coolest features, while any search for "edit vector nodes" and the like brings up lots of irrelevant results about node.js...

Probably you must have found the solution, but since it is unanswered, I thought of posting about a fantastic library I know.
The library is konva.js. You can find demo application references on site itself.
It features powerful set of functions to create custom shapes and layering support(In fact there is lot more). You can easily modify the properties of any shape, add animation and more.
You can find documentation here.

JS framework to create visual simulations on Canvas

I need to create some kind of simulation for example sorting algorithm on canvas. I need a JS framework which allow to transition or path transitions of some elements (i have no problem to calc coordinates), I don't want to use paperjs because I need simulation stepping (for example two elements switch) and use onFrame it's quite overhead for me, because I don't want to anything so much difficult, i need it for simple demo.

Have you looked at D3 (http://d3js.org/)?
Here is a blog post on using D3 with canvas http://bocoup.com/weblog/d3js-and-canvas/

How do I draw my Box2D world using HTML5 Canvas instead of Debug Draw?

I know HTML5 canvas fairly well, I know the basics and animation using loops etc.
Demo I'm working with: (click to make shapes) http://henry.brown.name/experiments/box2d/example-canvas.html
What I'm not very familiar with is Box2D. I'm using the Box2DWeb port, I heard it was newer than Box2D-js, I'm not sure which is best.
I know how to initialize the 'world' and I can place objects in the world. I then use Step to animate the world - however to display it on the screen so far I've only been able to get it working with debug draw as it basically does everything for you.
Instead of using debug draw I'd like to use canvas to draw, for example a car instead of just a square. How do I attach the physics of a square to the image of a car? I just can't get my head around integrating canvas with Box2D.
Any tips will be massively appreciated!
Thanks

I spent the last few days trying the same thing.
I found Jonny Strömberg's tutorial, which is not super detailled but by analyzing the code I found how he retrieves the body's position:
var b = world.GetBodyList()
GetBodyList() seems to be an iterative Array, so the next body is accessible through b.m_next.
You can then use
b.GetPosition().x
b.GetPosition().y
b.GetAngle()
to retrieve the body's coordinates.
EDIT: this code is for the Box2dweb library, which I found better documented than Box2djs

If you aren't familiar with Box2D you should check out the documentation at http://www.kyucon.com/doc/box2d/. This should tell you all of the properties you need. To my knowledge the standard way of using Box2D is to attach an image with userData. See this example tutorial for image and Canvas image usage.
http://www.jeremyhubble.com/box2d.html

I had the same question.
here is the documentation of it.
You could use calls like GetBodyList() , GetAngle()and members like m_position to get all that you need to paint whatever using whatever library you want to use on a canvas.

How to make a rotating object (sphere, box, etc.) using only the canvas

I'd like to make a rotating object (sphere, box, etc.) using only the canvas. But I can't find a tutorial. Help If you saw somewhere or explain how to do it.
Like this example, only without any effects

Hope you like math. 3D effects can always be achieved on a 2D plane if you are willing to write some code.
Some resources that will probably help:
An Intro to Computer Graphics
and for help with the math,
A Book on Linear Algebra

Ah well it's pretty simple in theory. One way is to just set up a timer and then when it fires, clear the canvas and redraw your sphere, box whatever. To make it faster you can cover over a region of the canvas instead of the whole thing. Also you can get png sprites and move them about on the canvas.
I got into this stuff by trying out the pyjamas canvas wrapper, which means you can code in python and then compile it into js, which to me is a lot friendlier.
http://pyjs.org/examples/gwtcanvas/output/GWTCanvasDemo.html
NB the demo is slightly borken but the example code does compile and run perfectly well if you do a git pull.