Error.prototype.toString()

The toString() method returns a string representing the specified Error object.

Syntax

toString()

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 (assuming Object and String have their original values):

Error.prototype.toString = function() {
  'use strict';

  var obj = Object(this);
  if (obj !== this) {
    throw new TypeError();
  }

  var name = this.name;
  name = (name === undefined) ? 'Error' : String(name);

  var msg = this.message;
  msg = (msg === undefined) ? '' : String(msg);

  if (name === '') {
    return msg;
  }
  if (msg === '') {
    return name;
  }

  return name + ': ' + msg;
};

Examples

Using toString()

var e1 = new Error('fatal error');
console.log(e1.toString()); // 'Error: fatal error'

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

var e3 = new Error('fatal error');
e3.name = '';
console.log(e3.toString()); // 'fatal error'

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

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

Specifications

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
toString
1
12
1
6
4
1
1
18
4
10.1
1
1.0

See also

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error/toString