backslash in string doesn't get escaped

[namedots]

This is causing misleading assertion messages on codewars.com whom I do not represent, but that's where I'm coming from:

TLDR: '\n' and '\\n' are represented the same. the rest of this poorly formatted post is just showing my work, hopefully that works for you.

import { assert } from 'chai'
assert.strictEqual('\n', '\\n')

part of output:

...
AssertionError: expected '\n' to equal '\n'
...

where the line terminator is escaped, but the backslash is NOT

so I grep around a bit in chai, and see this kind of thing:
129: , 'expected #{this} to equal #{exp}'
alright, so there's some home-grown string interpolation, seems promising, I keep following this..

  msg = msg
    .replace(/#\{this\}/g, function () { return objDisplay(val); })
    .replace(/#\{act\}/g, function () { return objDisplay(actual); })
    .replace(/#\{exp\}/g, function () { return objDisplay(expected); });

... keep following into loupe (now leaving chai)

var stringEscapeChars = new RegExp(
  "['\\u0000-\\u001f\\u007f-\\u009f\\u00ad\\u0600-\\u0604\\u070f\\u17b4\\u17b5\\u200c-\\u200f\\u2028-\\u202f\\u2060-\\u206f\\ufeff\\ufff0-\\uffff]",
  "g"
);
var escapeCharacters = {
  "\b": "\\b",
  "	": "\\t",
  "\n": "\\n",
  "\f": "\\f",
  "\r": "\\r",
  "'": "\\'",
  "\\": "\\\\"
};
var hex = 16;
var unicodeLength = 4;
function escape(char) {
  return escapeCharacters[char] || `\\u${`0000${char.charCodeAt(0).toString(hex)}`.slice(-unicodeLength)}`;
}
function inspectString(string, options) {
  if (stringEscapeChars.test(string)) {
    string = string.replace(stringEscapeChars, escape);
  }
  return options.stylize(`'${truncate(string, options.truncate - 2)}'`, "string");
}

alright, let me try that regex

> var stringEscapeChars = new RegExp(
...   "['\\u0000-\\u001f\\u007f-\\u009f\\u00ad\\u0600-\\u0604\\u070f\\u17b4\\u17b5\\u200c-\\u200f\\u2028-\\u202f\\u2060-\\u206f\\ufeff\\ufff0-\\uffff]",
...   "g"
... );
undefined
> stringEscapeChars.test('\n')
true
> stringEscapeChars.test('\\')
false

so I'm guessing that's it.
and then trying just loupe by itself:

    "node_modules/loupe": {
      "version": "3.1.2",
      "resolved": "https://registry.npmjs.org/loupe/-/loupe-3.1.2.tgz",
      "integrity": "sha512-23I4pFZHmAemUnz8WZXbYRSKYj801VDaNv9ETuMh7IrMc7VuVVSo+Z9iLE3ni30+U48iDWfi30d3twAXBYmnCg=="
    }

import {inspect} from 'loupe'
let a = inspect('\n')
let b = inspect('\\n')
console.log({a, b})

{ a: "'\\n'", b: "'\\n'" }

yeah.

[namedots]

oh yes, and also:

import { assert } from 'chai'
assert.strictEqual('#{exp}', 'atnouh')

expected ''atnouh'' to equal 'atnouh'

maybe that ought to be its own issue, idk

(and that's because of chai's:

  msg = msg
    .replace(/#\{this\}/g, function () { return objDisplay(val); })
    .replace(/#\{act\}/g, function () { return objDisplay(actual); })
    .replace(/#\{exp\}/g, function () { return objDisplay(expected); });

)