RegExp.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 RegExp instances returns a string representing this regular expression.

Try it

console.log(new RegExp("a+b+c"));
// Expected output: /a+b+c/

console.log(new RegExp("a+b+c").toString());
// Expected output: "/a+b+c/"

console.log(new RegExp("bar", "g").toString());
// Expected output: "/bar/g"

console.log(new RegExp("\n", "g").toString());
// Expected output: "/\n/g"

console.log(new RegExp("\\n", "g").toString());
// Expected output: "/\n/g"

Syntax

toString()

The RegExp object overrides the toString() method of the Object object; it does not inherit Object.prototype.toString(). For RegExp objects, the toString() method returns a string representation of the regular expression.

In practice, it reads the regex's source and flags properties and returns a string in the form /source/flags. The toString() return value is guaranteed to be a parsable regex literal, although it may not be the exact same text as what was originally specified for the regex (for example, the flags may be reordered).

Examples

Using toString()

The following example displays the string value of a RegExp object:

js
const myExp = new RegExp("a+b+c");
console.log(myExp.toString()); // '/a+b+c/'

const foo = new RegExp("bar", "g");
console.log(foo.toString()); // '/bar/g'

Empty regular expressions and escaping

Since toString() accesses the source property, an empty regular expression returns the string "/(?:)/", and line terminators such as \n are escaped. This makes the returned value always a valid regex literal.

js
new RegExp().toString(); // "/(?:)/"

new RegExp("\n").toString() === "/\\n/"; // true

Specifications

Specification

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

Browser compatibility

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Standard built-in objects
RegExp
Constructor
1. RegExp()
Static methods
1. escape()
Static properties
Instance methods
Instance properties
Inheritance
Object/Function
Static methods
Static properties
Instance methods
Instance properties
1. __proto__
2. constructor

RegExp.prototype.toString()

In this article

Try it

Syntax

Parameters

Return value

Description