bandolier-template/client/assert.js

/*
  A stupid thing I wrote so I could have the same assert function in the browser that I
  have in Node. This should just be standard in JavaScript.
 */
import { log } from "./logging.js";

/*
  This is the error that is thrown when an `assert()` fails.
 */
export class AssertionError extends Error {

  /*
    This is from https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error
    which claims you have to do this weird stuff to make your error actually work.
   */
  constructor(...params) {
    // Pass remaining arguments (including vendor specific ones) to parent constructor
    super(...params);

    // Maintains proper stack trace for where our error was thrown (only available on V8)
    if (Error.captureStackTrace) {
      // this "only on V8" is managed by the Error.captureStackTrace test above
      Error.captureStackTrace(this, AssertionError);
    }

    this.name = 'AssertionError';
    // Custom debugging information
    this.date = new Date();
  }
}

/*
  If `test` is false then it logs the message and raises the `AssertionError`.

  ___TODO___: Implement a way to "compile out" these assertions.

  + `test boolean` -- The code only does `if(!test)` so should work with most any falsy thing.
  + `message string` -- The message to log and then attach to the thrown `AssertionError`.
  + ___throws___ `AssertionError(message)`
 */
export const assert = (test, message) => {
  if(!test) {
    log.assert(test, message);
    throw new AssertionError(message);
  }
}

export default assert;