JavaScript-eval中的嵌套函数不适用于try / catch块

Question

I have the following code to run in an eval() :

const code = `
    async function func() {
        asd();
    }

    func();
`;

try {
    console.log("running code");
    return eval(code);
}
catch (err) {
    console.log("error");
    return err.message;
}

In this case, asd is undefined , and so I would expect a reference error to be returned as a string ( return err.message; ). However, instead of the catch block firing, an exception is thrown as if there is no try/catch block. But, if I were to run eval("asd()") , the catch block would catch the error and return a string. Is there something different I need to do for nested functions?

Note: This entire code is in an async function due to other code (before const code ... ), if that makes a difference.

Answer 1

You need to handle eval as a promise since you are using a promise inside it.

 const asyncEval = () => { const code = ` async function func() { asd(); } func(); `; console.log("running code"); return Promise.resolve(eval(code)); } const ele = document.getElementById('result'); asyncEval() .then(res => { ele.innerText = res; }) .catch(err => { ele.innerText = "ERROR: " + err; }) 

 <pre id="result"></pre> 

To ensure it works if there is a promise returned or not you can do Promise.resolve(eval(code)) instead of eval(code) .

Either way, I would also recommend reading this and not using eval: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/eval#Do_not_ever_use_eval !