AJAX and Canvas

Question

Hello,
i'm experimenting a bit with an esp32 and a network.
The ESP32 measures a temperature which I then display on a web page. This works with AJAX etc.
The temperature value is cyclically sent and displayed.
Now I want to display the temperature as a graph.
For example with a pointer.
Can anyone help me with a simple example?
I do not understand the use of CANVAS in this problem.

many thanks and greetings

Answer 1

Do you wanna draw something like a chart ?

I think you can use chart.js

https://code.sololearn.com/WeD60RcuAtZ3/?ref=app

Answer 2

See this video
https://youtu.be/PVPQR7tMtHc

Do you want something like this ?

Answer 3

See this Canvas Tutorial
https://www.sololearn.com/learn/HTML/2201/

Answer 4

https://www.sololearn.com/learn/HTML/2201/

Das geht nicht...

Answer 5

Hello,
Thanks for the info.
Unfortunately the first link does not work.
I understand how something is drawn with canvas, it works too.
Unfortunately I can't manage to update the canvas drawing regularly. This is my problem.
The numerical values are updated, that works.

Regards...

Answer 6

Hi,

thanks for the Example.
Here is my Code:
https://code.sololearn.com/WNA2eThYsZq8/#html

A canvas drawing area is created and a red rectangle and line are drawn.
I want the line to be drawn differently depending on the value. So like a hand of a clock.
I do not want to work with the Chart Lib.
It is called GetAjaxData every 250ms and the values are displayed as numbers. I would like to draw a pointer parallel to this.

greetings...