如何在没有eval的情况下检测异步功能支持? [英] How to detect async function support without eval?

问题描述

这是一种检测当前引擎是否支持异步功能的方法:

Here's one way to detect if the current engine supports async functions:

const supportsAsyncFunctions = (() => {
  try {
    new Function('async () => {}')();
  } catch (error) {
    return false;
  }

  return true;
})();

但是有没有不用eval或Function的方法吗?

But is there a way to do it without using eval or Function?

推荐答案

建议的eval方法将为CSP错误提供错误否定，因为它们没有得到处理.如果这是一个问题，则可以按照

Suggested eval way will give false negatives for CSP errors because they are not handled. If this is a problem, CSP errors can be handled as shown in this answer.

可以这样做，但是解决方案一点也不漂亮，涉及到外部脚本.该脚本可以设置标志，也可以设置全局错误处理程序以在加载脚本时监视语法错误.

It is possible to do that, but the solution is not pretty at all and involves external script. The script can set a flag, or global error handler can be set up to watch for syntax errors when the script is loaded.

如果脚本导致语法错误，则仍然认为该脚本已加载，因此网络问题不会导致误报:

If the script results in syntax error, it is still considered loaded, so network problems cannot cause false positives:

async-detection.js

window.isAsyncAvailable = true;
async () => {};

main.js

new Promise(function (resolve, reject) {
  var script = document.createElement('script');
  document.body.appendChild(script);
  script.onload = resolve.bind(null, true);
  script.onerror = reject;
  script.async = true;
  script.src = 'async-detection.js';
})
.then(function () {
  console.log(window.isAsyncAvailable);
})
.catch(/* generic script loading error */);

此方法可用于检测网站上使用的语法功能，这些语法功能不能被try..catch填充或正常捕获.可靠地触发您的浏览器已过时导航屏幕特别有用.

This method can be used to detect syntactic features used on the website that cannot be polyfilled or normally caught with try..catch. It is particularly useful to reliably trigger Your browser is outdated nag screen.

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