How to save stage of canvas in JSON format?

In my current project I want to build something like Image Editor with react and react-konva.

First of all, I render a konva stage with some props and default draggable stars.

In the next step we can set background image for our stage using Image from react-konva.

<Stage width={konvaWidth} height={height - 150} className={classes.canvas} onClick={test}>
        <Layer>
          {image && bg && <Image
            x={0}
            y={0}
            image={bg}
            scaleX={0.35}
            scaleY={0.35}
            ref={node => {
              imageRef = node;
            }}
          />}
          <Text text="Try to drag a star" />
          {[...Array(10)].map((_, i) => (
            <Star
              key={i}
              x={Math.random() * window.innerWidth}
              y={Math.random() * window.innerHeight}
              numPoints={5}
              innerRadius={20}
              outerRadius={40}
              fill="#89b717"
              opacity={0.8}
              draggable
              rotation={Math.random() * 180}
              shadowColor="black"
              shadowBlur={10}
              shadowOpacity={0.6}
              onDragStart={handleDragStart}
              onDragEnd={handleDragEnd}
            />
          ))}
        </Layer>
      </Stage>

The next, and finally step.

Can we save konva stage to json format?

The Konva API has toJSON() method. You can convert any node (like Stage) into json.

https://konvajs.org/docs/data_and_serialization/Serialize_a_Stage.html

For more complex cases (like if you have images, filters): https://konvajs.org/docs/data_and_serialization/Best_Practices.html

BUT if you are using react I don't recommend to use Konva methods to serialize the canvas rendering.

In your react you must have a state of your app. In can be any state library (mobx, redux) or just setState or useState of React or anything else. Usually, that state is easily serializable to JSON.