HTML5 Canvas How to avoid Memory leaks Tip

Deleting shapes

There are two very close methods remove() and destroy(). If you need to completely delete a node you should destroy() it. The destroy() method deletes all references to node from the KonvaJS engine. If you are going to reuse a node you should remove() it then later you can add it again to any container.

Tweening

When you are using Konva.Tween instance you have to destroy it after usage.

Here's a demo showing proper memory management:

Vanilla

import Konva from 'konva';

const stage = new Konva.Stage({
  container: 'container',
  width: window.innerWidth,
  height: window.innerHeight,
});

const layer = new Konva.Layer();
stage.add(layer);

// Create circle
const circle = new Konva.Circle({
  x: 100,
  y: 100,
  radius: 30,
  fill: 'red'
});

layer.add(circle);

// Add buttons
const addButton = document.createElement('button');
addButton.textContent = 'Add Circle';
document.body.appendChild(addButton);

const removeButton = document.createElement('button');
removeButton.textContent = 'Remove Circle';
document.body.appendChild(removeButton);

const animateButton = document.createElement('button');
animateButton.textContent = 'Animate';
document.body.appendChild(animateButton);

// Handle adding/removing
addButton.addEventListener('click', () => {
  layer.add(circle);
  layer.draw();
});

removeButton.addEventListener('click', () => {
  // Just remove from layer, can be added back
  circle.remove();
  layer.draw();
});

animateButton.addEventListener('click', () => {
  // Using to() method which auto-destroys the tween
  circle.to({
    x: Math.random() * stage.width(),
    y: Math.random() * stage.height(),
    duration: 1
  });
  
  // If using Tween directly, make sure to destroy it
  const tween = new Konva.Tween({
    node: circle,
    rotation: 360,
    duration: 1,
    onFinish: function() {
      // Clean up the tween
      tween.destroy();
    }
  }).play();
});

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React

import { Stage, Layer, Circle } from 'react-konva';
import { useState } from 'react';

const App = () => {
  const [isVisible, setIsVisible] = useState(true);
  const [position, setPosition] = useState({ x: 100, y: 100 });
  const [rotation, setRotation] = useState(0);

  const handleAdd = () => {
    setIsVisible(true);
  };

  const handleRemove = () => {
    setIsVisible(false);
  };

  const handleAnimate = () => {
    // Update position
    setPosition({
      x: Math.random() * window.innerWidth,
      y: Math.random() * window.innerHeight
    });
    
    // Update rotation
    setRotation(rotation + 360);
  };

  return (
    <div>
      <button onClick={handleAdd} style={{ marginRight: '10px' }}>Add Circle</button>
      <button onClick={handleRemove} style={{ marginRight: '10px' }}>Remove Circle</button>
      <button onClick={handleAnimate}>Animate</button>
      
      <Stage width={window.innerWidth} height={window.innerHeight}>
        <Layer>
          {isVisible && (
            <Circle
              x={position.x}
              y={position.y}
              radius={30}
              fill="red"
              rotation={rotation}
            />
          )}
        </Layer>
      </Stage>
    </div>
  );
};

export default App;

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Vue

<template>
  <div>
    <button @click="handleAdd" style="margin-right: 10px">Add Circle</button>
    <button @click="handleRemove" style="margin-right: 10px">Remove Circle</button>
    <button @click="handleAnimate">Animate</button>
    
    <v-stage :config="stageSize">
      <v-layer>
        <v-circle
          v-if="isVisible"
          :config="circleConfig"
        />
      </v-layer>
    </v-stage>
  </div>
</template>

<script setup>
import { ref } from 'vue';

const stageSize = {
  width: window.innerWidth,
  height: window.innerHeight
};

const isVisible = ref(true);
const position = ref({ x: 100, y: 100 });
const rotation = ref(0);

const circleConfig = ref({
  x: position.value.x,
  y: position.value.y,
  radius: 30,
  fill: 'red',
  rotation: rotation.value
});

const handleAdd = () => {
  isVisible.value = true;
};

const handleRemove = () => {
  isVisible.value = false;
};

const handleAnimate = () => {
  // Update position
  position.value = {
    x: Math.random() * window.innerWidth,
    y: Math.random() * window.innerHeight
  };
  
  // Update rotation
  rotation.value += 360;
  
  // Update config
  circleConfig.value = {
    ...circleConfig.value,
    x: position.value.x,
    y: position.value.y,
    rotation: rotation.value
  };
};
</script>

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