how to save an image from a canvas in js?
To save an image from a Canvas in JavaScript, you can use the canvas's context2d API. The following code demonstrates how to draw a circle onto the canvas and then use the save() method to save the image as a PNG file:
```js
const canvas = document.querySelector("canvas"); // Get the canvas element
var ctx = canvas.getContext("2d");  // Create a 2D rendering context for the canvas

// Draw a circle on the canvas using the fill() method
ctx.fillCircle(100, 100, 50);

// Save the image to a local file system (e.g., "image.png") 
canvas.toDataURL("image/png", 0.9 /*quality*/)
   .then((dataurl) => console.log(`Image saved to ${dataurl}`));
```