在JavaScript中不使用throw语句能否抛出自定义错误？

Great question! Let’s break this down based on whether you need a synchronous or asynchronous error:

Asynchronous Custom Error (No throw, eval, Function, or Error keyword) #

Yes, you can trigger a catchable exception without writing the throw statement yourself, and even without using the Error keyword. The trick is using async/await with Promise.reject()—since await converts a rejected promise into a thrown exception automatically.

Here’s a working example:

async function triggerCustomError() {
  // Reject with any custom value (string, object, etc.)
  await Promise.reject("Oops, this is my custom error message!");
}

try {
  await triggerCustomError();
} catch (e) {
  console.log("Caught error:", e); // Outputs: Caught error: Oops, this is my custom error message!
}

This works because when you await a rejected promise, the JavaScript engine throws the rejection reason into the surrounding try/catch block—no throw statement required. Since we’re rejecting with a plain string, we don’t need the Error keyword at all.

Synchronous Custom Error #

Unfortunately, there’s no way to throw a synchronous custom error (with a message or type you control) without using the throw statement. All built-in synchronous exceptions (like ReferenceError, TypeError, etc.) have predefined, uncustomizable messages. For example, accessing null.property throws a TypeError with a fixed message, but you can’t alter that message to something custom without using throw.

Bonus: Using an Error object without the Error keyword #

If you want to throw a proper Error instance (for stack traces, etc.) but avoid writing the Error keyword directly, you can access it via the global object using bracket notation:

async function triggerProperError() {
  // Get the Error constructor without using the keyword
  const ErrorConstructor = window['Error'];
  await Promise.reject(new ErrorConstructor("Custom error with stack trace"));
}

try {
  await triggerProperError();
} catch (e) {
  console.log("Error message:", e.message);
  console.log("Stack trace:", e.stack);
}

This still avoids throw, eval, and Function, and skips using the Error keyword explicitly.

内容的提问来源于stack exchange，提问作者Muhammad Salman