这里的问题是，web工作人员在一个非常孤立的环境中运行，在这个环境中，网站上运行的javascript的许多标准全局变量（窗口、文档等）都不存在，不幸的是，如果没有这些变量，p5.js无法加载。你可以试着用假版本来填充它们。以下是一个基本示例：

let loadHandlers = [];

window = {
  performance: performance,
  document: {
    hasFocus: () => true,
    createElementNS: (ns, elem) => {
      console.warn(`p5.js tryied to created a DOM element '${ns}:${elem}`);
      // Web Workers don't have a DOM
      return {};
    }
  },
  screen: {},
  addEventListener: (e, handler) => {
    if (e === "load") {
      loadHandlers.push(handler);
    } else {
      console.warn(`p5.js tried to added an event listener for '${e}'`);
    }
  },
  removeEventListener: () => {},
  location: {
    href: "about:blank",
    origin: "null",
    protocol: "about:",
    host: "",
    hostname: "",
    port: "",
    pathname: "blank",
    search: "",
    hash: ""
  }
};

document = window.document;
screen = window.screen;

// Without a setup function p5.js will not declare global functions
window.setup = () => {
  window.noCanvas();
  window.noLoop();
};

importScripts("/p5.js");

// Initialize p5.js
for (const handler of loadHandlers) {
  handler();
}

postMessage({ color: "green" });

onmessage = msg => {
  if (msg.data === "getRandomColor") {
    // p5.js places all of its global declarations on window
    postMessage({
      color: window.random([
        "red",
        "limegreen",
        "blue",
        "magenta",
        "yellow",
        "cyan"
      ])
    });
  }
};

这只适用于p5.js函数的有限子集。任何绘制到画布上的函数都肯定不起作用。我会谨慎地尝试来回传递对象（即p5.vector、p5.color等），因为通过postmessage发送的所有内容都会被序列化和反序列化。
我已经在glitch上发布了这个示例的工作版本。