The toString() method of RegExp instances returns a string representing this regular expression.
Syntax
toString()
Parameters
None.
Return value
A string representing the given object.
Description
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:
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.
new RegExp().toString(); // "/(?:)/"
new RegExp("\n").toString() === "/\\n/"; // true