How can I use Fabric.js with React?

We had this same issue in our app of how to use Fabric.js inside of react. My recommendation is to treat fabric as an uncontrolled component. Have fabric instance that your whole app can talk to and make fabric calls and then when anything changes use .toObject() call to put the whole fabric state into your Redux store. Then your React app can read fabric state from your global Redux state as you would do in any normal React app.

I can't get an example working in the StackOverflow code editor but here is a JSFiddle example that implements the pattern I am recommending.

I've used Fabric for a proof-of-concept project and the general idea is the same as for, say, D3. Keep in mind that Fabric operates over DOM elements, while React renders data into DOM, and usually the latter is deferred. There are two things that will help you make sure your code works:

Wait until component is mounted

To do that, place your Fabric instantiation into componentDidMount:

import React, { Component } from 'react';
import { fabric } from 'react-fabricjs';
import styles from './MyComponent.css';

class MyComponent extends Component {
  componentWillMount() {
    // dispatch some actions if you use Redux
  }

  componentDidMount() {
    const canvas = new fabric.Canvas('c');

    // do some stuff with it
  }

  render() {
    return (
      <div className={styles.myComponent}>
        <canvas id="c" />
      </div>
    )
  }
}

Placing Fabric constructor into componentDidMount ensures it won't fail because by the moment this method is executed, the DOM is ready. (but the props sometimes aren't, just in case if you use Redux)

Use refs to calculate actual width and height

Refs are references to actual DOM elements. You can do with refs what you can do with DOM elements using DOM API: select children, find parent, assign style properties, calculate innerHeight and innerWidth. The latter is precisely what you need:

componentDidMount() {
  const canvas = new fabric.Canvas('c', {
    width: this.refs.canvas.clientWidth,
    height: this.refs.canvas.clientHeight
  });

  // do some stuff with it
}

Don't forget to define refs property of this. To do that, you'll need a constructor. The whole thing would look like

import React, { Component } from 'react';
import { fabric } from 'react-fabricjs';
import styles from './MyComponent.css';

class MyComponent extends Component {
  constructor() {
    super()
    this.refs = {
      canvas: {}
    };
  }

  componentWillMount() {
    // dispatch some actions if you use Redux
  }

  componentDidMount() {
    const canvas = new fabric.Canvas('c', {
      width: this.refs.canvas.clientWidth,
      height: this.refs.canvas.clientHeight
    });

    // do some stuff with it
  }

  render() {
    return (
      <div className={styles.myComponent}>
        <canvas
          id="c"
          ref={node => {
            this.refs.canvas = node;
          } />
      </div>
    )
  }
}

Mix Fabric with component state or props

You can make your Fabric instance react to any component props or state updates. To make it work, simply update your Fabric instance (which, as you could see, you can store as part of component's own properties) on componentDidUpdate. Simply relying on render function calls won't be really helpful because none of the elements that are rendered would ever change on new props or new state. Something like this:

import React, { Component } from 'react';
import { fabric } from 'react-fabricjs';
import styles from './MyComponent.css';

class MyComponent extends Component {
  constructor() {
    this.refs = {
      canvas: {}
    };
  }

  componentWillMount() {
    // dispatch some actions if you use Redux
  }

  componentDidMount() {
    const canvas = new fabric.Canvas('c', {
      width: this.refs.canvas.clientWidth,
      height: this.refs.canvas.clientHeight
    });

    this.fabric = canvas;

    // do some initial stuff with it
  }

  componentDidUpdate() {
    const {
      images = []
    } = this.props;
    const {
      fabric
    } = this;

    // do some stuff as new props or state have been received aka component did update
    images.map((image, index) => {
      fabric.Image.fromURL(image.url, {
        top: 0,
        left: index * 100 // place a new image left to right, every 100px
      });
    });
  }

  render() {
    return (
      <div className={styles.myComponent}>
        <canvas
          id="c"
          ref={node => {
            this.refs.canvas = node;
          } />
      </div>
    )
  }
}

Simply replace image rendering with the code you need and that depends on new component state or props. Don't forget to clean up the canvas before rendering new objects on it, too!

With react 16.8 or newer you can also create a custom hook:

import React, { useRef, useCallback } from 'react';
const useFabric = (onChange) => {
    const fabricRef = useRef();
    const disposeRef = useRef();
    return useCallback((node) => {
        if (node) {
            fabricRef.current = new fabric.Canvas(node);
            if (onChange) {
                disposeRef.current = onChange(fabricRef.current);
            }
        }
        else if (fabricRef.current) {
            fabricRef.current.dispose();
            if (disposeRef.current) {
                disposeRef.current();
                disposeRef.current = undefined;
            }
        }
    }, []);
};

Usage

const FabricDemo = () => {
  const ref = useFabric((fabricCanvas) => {
    console.log(fabricCanvas)
  });
  return <div style={{border: '1px solid red'}}>
    <canvas ref={ref} width={300} height={200} />
  </div>
}

I don't see any answers here using React's functional components, and I couldn't get the hook from @jantimon to work. Here's my approach. I have the canvas itself take its dimensions from the layout of the page, then have a "backgroundObject" at (0,0) that acts as the drawable area for the user.

import React, { useState, useRef, useEffect } from 'react';

const { fabric } = window;

// this component takes one prop, data, which is an object with data.sizePixels, an array that represents the width,height of the "backgroundObject"

const CanvasComponent = ({ data }) => {
  const canvasContainer = useRef();
  const canvasRef = useRef();
  const fabricRef = useRef();
  const [error, setError] = useState();

  const initCanvas = ({ canvas, size }) => {
    console.log('*** canvas init');
    console.log(canvas);

    let rect = new fabric.Rect({
      width: size[0],
      height: size[1],
      fill: 'white',
      left: 0,
      top: 0,
      selectable: false,
      excludeFromExport: true,
    });
    canvas.add(rect);

    rect = new fabric.Rect({
      width: 100,
      height: 100,
      fill: 'red',
      left: 100,
      top: 100,
    });
    canvas.add(rect);
  };

  // INIT
  useEffect(() => {
    if (!canvasRef.current) return;
    if (fabricRef.current) return;
    const canvas = new fabric.Canvas('canvas', {
      width: canvasContainer.current.clientWidth,
      height: canvasContainer.current.clientHeight,
      selection: false, // disables drag-to-select
      backgroundColor: 'lightGrey',
    });
    fabricRef.current = canvas;
    initCanvas({ canvas, size: data.sizePixels });
  });

  // INPUT CHECKING
  if (!data || !Array.isArray(data.sizePixels)) setError('Sorry, we could not open this item.');

  if (error) {
    return (
      <p>{error}</p>
    );
  }

  return (
    <>
      <div style={{
        display: 'flex',
        flexDirection: 'row',
        width: '100%',
        minHeight: '60vh',
      }}
      >
        <div style={{ flex: 3, backgroundColor: 'green' }}>
          Controls
        </div>
        <div ref={canvasContainer} style={{ flex: 7, backgroundColor: 'white' }}>
          <canvas id="canvas" ref={canvasRef} style={{ border: '1px solid red' }} />
        </div>
      </div>

      <div>
        <button
          type="button"
          onClick={() => {
            const json = fabricRef.current.toDatalessJSON();
            setDebugJSON(JSON.stringify(json, null, 2));
          }}
        >
          Make JSON
        </button>
      </div>
    </>
  );
};

export default CanvasComponent;

There is also react-fabricjs package which allows you to use fabric objects as react components. Actually, Rishat's answer includes this package, but I don't understand how it is supposed to work as there is no 'fabric' object in the react-fabricjs (he probably meant 'fabric-webpack' package). An example for simple 'Hello world' component:

import React from 'react';
import {Canvas, Text} from 'react-fabricjs';

const HelloFabric = React.createClass({
  render: function() {
    return (
      <Canvas
        width="900"
        height="900">
          <Text
            text="Hello World!"
            left={300}
            top={300}
            fill="#000000"
            fontFamily="Arial"
          />
      </Canvas>
    );
  }
});

export default HelloFabric;

Even if you don't want to use this package, exploring it's code might help you to understand how to implement Fabric.js in React by yourself.