The source property returns a String containing the source text of the regexp object, and it doesn't contain the two forward slashes on both sides and any flags.

Try it

Property attributes of RegExp.prototype.source
Writable no
Enumerable no
Configurable yes


Using source

const regex = /fooBar/ig;

console.log(regex.source); // "fooBar", doesn't contain /.../ and "ig".

Empty regular expressions and escaping

Starting with ECMAScript 5, the source property no longer returns an empty string for empty regular expressions. Instead, the string (?:) is returned. In addition, line terminators (such as "\n") are escaped now.

new RegExp().source; // "(?:)"

new RegExp('\n').source === '\n';  // true, prior to ES5
new RegExp('\n').source === '\\n'; // true, starting with ES5


ECMAScript Language Specification
# sec-get-regexp.prototype.source

Browser compatibility

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See also