cacnelable-async.js

const acorn = require("acorn");
const astring = require("astring");
const estraverse = require("estraverse");

function withCancel(func) {
  const signalName = "__$isCancel__";
  const shouldCancelName = "__$shouldCancel__";

  function transform(node) {
    return estraverse.replace(node, {
      enter(node) {
        if (/function/i.test(node.type)) {
          return estraverse.VisitorOption.Skip;
        }
        return node;
      },
      leave(node) {
        if (node.type === "AwaitExpression") {
          return {
            type: "CallExpression",
            callee: {
              type: "Identifier",
              name: shouldCancelName,
            },
            arguments: [node],
          };
        }
        return node;
      },
    });
  }

  const ast = acorn.parse(func.toString(), {});
  ast.body[0].expression.body = transform(ast.body[0].expression.body);

  const funcCode = astring.generate(ast).replace(/;\s*$/, "");
  return `((function () {
    var ${signalName} = false;
    function ${shouldCancelName}(value) { 
      if (${signalName}) throw new Error('Cancel'); 
      return value;
    };
    return [${funcCode}, function (){ ${signalName} = true }];
  })())`;
}

function delay(t) {
  return new Promise((resolve) => setTimeout(resolve, t));
}

async function __main__() {
  const [a, cancelA] = eval(
    withCancel(async () => {
      for (let i = 0; i < 10; i++) {
        await delay(1e3);
        console.log(i);
      }
    })
  );
  try {
    setTimeout(cancelA, 4e3);
    await a();
  } catch (error) {
    if (error.message === "Cancel") {
      console.log(error.message);
    }
  }
}

__main__();