New JavaScript Proposals Transform Error Handling, RegExp, and Binary Data

When a proposal reaches Stage 3, browsers and Node.js begin implementing its features, and changes are rare unless major issues arise.

Error.isError

Proposal: proposal-is-error . It introduces a global method Error.isError to accurately determine whether a value is an Error object. The need arises because Symbol.toStringTag can make Object.prototype.toString() return unreliable strings.

Using a fabricated FakeError class that returns 'Error' from its [Symbol.toStringTag] getter, the method can correctly identify both real Error instances and faked ones:

class FakeError {
  get [Symbol.toStringTag]() {
    return 'Error';
  }
}

// Output: [object Error]
console.log(Object.prototype.toString.call(new FakeError()));
// Output: [object Error]
console.log(Object.prototype.toString.call(new Error()));
// Output: true
console.log(Object.prototype.toString.call(new Error()) === Object.prototype.toString.call(new FakeError()));

The popular is-error package implements the same check with Object.prototype.toString() === '[object Error]'.

RegExp.escape

Proposal: proposal-regex-escaping . Developers often need to build regular expressions from strings without treating special characters as regex tokens, but no built‑in method exists.

Example of the problem:

let text = "Hello.";
// this would match . against any character rather than matching it against a dot
ourLongText.replace(new RegExp(text, "g"));

Escaping user input is also required for security, yet existing implementations may miss some characters or mishandle multi‑code‑unit UTF‑8 symbols (e.g., '😂'.length === 2).

The proposal adds RegExp.escape to escape all regex‑special characters:

const str = prompt("Please enter a string");
const escaped = RegExp.escape(str);
const re = new RegExp(escaped, 'g'); // handles reg exp special tokens with the replacement.
console.log(ourLongText.replace(re));

Examples:

RegExp.escape("The Quick Brown Fox"); // "The Quick Brown Fox"
RegExp.escape("Buy it. use it. break it. fix it."); // "Buy it\. use it\. break it\. fix it\."
RegExp.escape("(*.*)"); // "\(\*\.\*\)"
RegExp.escape("｡^･ｪ･^｡"); // "｡\^･ｪ･\^｡"
RegExp.escape("😊 *_* +_+ ... 👍"); // "😊 \*_\* \+_\+ \.\.\. 👍"
RegExp.escape("\d \D (?:)"); // "\\d \\D \(\?:\)"

Uint8Array to/from base64 and hex

Proposal: proposal-arraybuffer-base64 . It adds binary‑data conversion methods to Uint8Array, enabling direct base64 and hexadecimal transformations.

Current JavaScript provides btoa and atob for string‑based base64, but they are limited to Latin‑1 encoded data. The proposal introduces Uint8Array.prototype.toBase64, Uint8Array.fromBase64, Uint8Array.prototype.toHex, and Uint8Array.fromHex for robust handling.

Base64 example:

const binaryData = new Uint8Array([72, 101, 108, 108, 111, 44, 32, 87, 111, 114, 108, 100, 33]);

// binary data → Base64 encoding
const base64Data = btoa(String.fromCharCode.apply(null, binaryData));
console.log(base64Data); // "SGVsbG8sIFdvcmxkIQ=="

// Base64 encoding → binary data
const decodedBinaryData = new Uint8Array(atob(base64Data).split('').map(function(c) {
    return c.charCodeAt(0);
}));
console.log(decodedBinaryData); // Uint8Array[ 72, 101, 108, 108, 111, 44, 32, 87, 111, 114, 108, 100, 33 ]

Using the new methods:

const raw = new Uint8Array([72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100]);
const str = raw.toBase64(); // 'SGVsbG8gV29ybGQ='
const arr = Uint8Array.fromBase64(str); // Uint8Array([72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100])

Time Zone Canonicalization

Proposal: proposal-canonical-tz . Time‑zone names in ECMAScript come from the IANA Time Zone Database, which is periodically updated. The proposal standardizes handling of updated zones, simplifies identifiers, and adds Temporal.TimeZone.prototype.equals to compare two zones for equivalence.

Temporal.TimeZone.from('Asia/Calcutta').equals('Asia/Kolkata'); // => true

References

proposal-is-error: https://github.com/tc39/proposal-is-error

proposal-regex-escaping: https://github.com/tc39/proposal-regex-escaping

proposal-arraybuffer-base64: https://github.com/tc39/proposal-arraybuffer-base64#uint8array-tofrom-base64-and-hex

proposal-canonical-tz: https://github.com/tc39/proposal-canonical-tz

Time Zone Database: https://www.iana.org/time-zones