RegExp.prototype.source

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.

var regex = /fooBar/ig;

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

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

• RegExp.prototype.flags