A tiny, dynamic type checker and TypeError generator

typeCheck.js

function checkTypes(...requiredArgs, expectedTypes) {
  var mistyped = requiredArgs.filter((argumentObj, index) => {
    return expectedTypes[index]
      ? !expectedTypes[index].includes(typeof Object.values(argumentObj)[0])
      : false;
  });
  if (mistyped != "") {
    throw new TypeError(
      `expected the argument "${
        Object.keys(mistyped[0])[0]
      }" to be of one of the following types: ${expectedTypes[
        requiredArgs
          .map((obj) => {
            return Object.keys(obj)[0];
          })
          .indexOf(Object.keys(mistyped[0])[0])
      ].reduce((previous, current, index, array) => {
        return (
          previous +
          current +
          (array.length > 1 && index !== array.length - 1
            ? index === array.length - 2
              ? ", or "
              : ", "
            : "")
        );
      }, "")}; got ${typeof Object.values(mistyped[0])[0]}`
    );
  }
}

Simply pass each variable you wish to check, one at a time, as its reference wrapped by braces. Finally, provide an array of arrays, each sub-array corresponding to one passed variable, and containing every type which that variable's value is allowed to take. If one of the variables is of a type not specified for it, a TypeError will be thrown. If multiple variables are invalid, the first one, in the order that they were passed, will be the one mentioned in the Error.

(This function was taken directly from the code of the Membrane project.)

//Example use-case

const x = "I'm a string."
const y = 8092834
const z = undefined
try {
  checkTypes({x}, {y}, {z}, [["string", "number"], ["number"], ["string", "object", "bigint"]])
} catch (error) {
  //Expected output: "TypeError: expected the argument "z" to be of one of the following types: string, object, or bigint; got undefined"
  console.warn(error)
}