How to throw an error without throw

Question

So recently I was asked a question :

Is there a way to throw an error without using throw in javaScript ?

As far as I knew about errors, there was only one way to throw an error in JavaScript and that was using throw statement in JavaScript like so :

var myFunc = () => {
  // some code here 
  throw 'Some error' // in a conditional 
  // some more code
}

try {
  myFunc()
}catch(e) {
  console.log(e)
}

And not knowing any other way I said No, there is no other way. But now I'm wondering whether I was right ?

So the question is whether or not you can throw a custom error in JavaScript without using throw

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Restrictions :

• Kindly no using eval , Function.
• Don't use throw in your code

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Additional :

If you can throw an error without using the word Error

Answer 1

Generators do have a throw method that is usually used to throw an exception into the generator function code (at the place of a yield expression, similar to next), but if not caught it bubbles out of the call:

(function*(){})().throw(new Error("example"))

Of course, this is a hack and not good style, I have no idea what answer they expected. Especially the "no division by zero" requirement is sketchy, since division by zero does not throw exceptions in JS anyway.

Answer 2

If all you want to do is throw an error then just do an invalid operation. I've listed a few below. Run them on your browser console to see the errors (tested on chrome and firefox).

var myFunc = () => {
  encodeURI('\uD800');    // URIError
  a = l;                  // ReferenceError
  null.f()                // TypeError
}


try {
  myFunc()
}catch(e) {
  console.log(e);
}

Answer 3

function throwErrorWithoutThrow(msg) {
  // get sample error 
  try {
    NaN();
  } catch (typeError) {
    // aquire reference to Error
    let E = typeError.__proto__.__proto__.constructor;

    // prepare custom Error
    let error = E(msg);

    // throw custom Error
    return Promise.reject(error);
  }
}

throwErrorWithoutThrow("hi")
  /* catch the error, you have to use .catch as this is a promise
  that's the only drawback, you can't use try-catch to catch these errors */
  .catch((e) => {
    console.log("Caught You!");
    console.error(e);
  });