Echartjs 中的 web worker 实现问题“无法在 'Worker' 上执行 'postMessage'：索引 0 处的值没有可转移类型。”

Question

can anyone help me to implement a web worker?

Main Code:

dataset = "dataset" + document.getElementById("dataset").value
      const config = {
        xAxis: {
          type: 'category',
          data: Object.keys(window[dataset])
        },
        yAxis: {
          type: 'value'
        },
        series: [
          {
            data: Object.values(window[dataset]),
            type: 'line'
          }
        ]
      };
      const worker1 = new Worker('worker/echarts1.worker.js');
      const canvasEl = document.getElementById("offscreenCanvas1");
      console.log(canvasEl);
      const offscreenCanvas = canvasEl.transferControlToOffscreen();
      worker1.postMessage({ canvas: offscreenCanvas, config }, [offscreenCanvas]);

Web Worker (echarts1.worker.js)

importScripts('https://cdn.jsdelivr.net/npm/echarts@5.3.3/dist/echarts.js');

onmessage = function (event) {
    console.log("Started Worker");
    const { canvas, config } = event.data;
    const chart = new echarts.init(canvas);
    chart.setOption(config);
    console.log("Finished Worker");
};

While Executing I'm facing the below error in the console.

Answer 1

You are transferring a (possible) HTMLCanvasElement ( <canvas> ), not an OffscreenCanvas.

To get the OffscreenCanvas out of that HTMLCanvasElement, you need to call its .transferControlToOffscreen() method:

const canvasEl = document.getElementById("chart-container1");
const offscreenCanvas = canvasEl.transferControlToOffscreen();
const worker1 = new Worker('echarts1.worker.js');
worker1.postMessage({ canvas: offscreenCanvas, config }, [offscreenCanvas]);

(If the element with an id ""chart-container1" isn't a <canvas> , then you need to target one instead.)