Error.prototype.toString()

Baseline Widely available

This feature is well established and works across many devices and browser versions. It's been available across browsers since July 2015.

The toString() method of Error instances returns a string representing this error.

Syntax

toString()

Parameters

None.

Return value

A string representing the specified Error object.

Description

The Error object overrides the Object.prototype.toString() method inherited by all objects. Its semantics are as follows:

Error.prototype.toString = function () {
  if (
    this === null ||
    (typeof this !== "object" && typeof this !== "function")
  ) {
    throw new TypeError();
  }
  let name = this.name;
  name = name === undefined ? "Error" : `${name}`;
  let msg = this.message;
  msg = msg === undefined ? "" : `${msg}`;
  if (name === "") {
    return msg;
  }
  if (msg === "") {
    return name;
  }
  return `${name}: ${msg}`;
};

Examples

Using toString()

const e1 = new Error("fatal error");
console.log(e1.toString()); // "Error: fatal error"

const e2 = new Error("fatal error");
e2.name = undefined;
console.log(e2.toString()); // "Error: fatal error"

const e3 = new Error("fatal error");
e3.name = "";
console.log(e3.toString()); // "fatal error"

const e4 = new Error("fatal error");
e4.name = "";
e4.message = undefined;
console.log(e4.toString()); // ""

const e5 = new Error("fatal error");
e5.name = "hello";
e5.message = undefined;
console.log(e5.toString()); // "hello"

Specifications

Specification
ECMAScript® 2027 Language Specification # sec-error.prototype.tostring

Browser compatibility

	Desktop					Mobile							Server
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on iOS	Samsung Internet	WebView Android	WebView on iOS	Bun	Deno	Node.js
`toString`	1	12	1	4	1	18	4	10.1	1	1.0	4.4	1	1.0.0	1.0	0.10.0