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RegExp.prototype.source

The source accessor property of RegExp instances returns a string containing the source text of this regular expression, without the two forward slashes on both sides or any flags.

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Description

Conceptually, the source property is the text between the two forward slashes in the regular expression literal. The language requires the returned string to be properly escaped, so that when the source is concatenated with a forward slash on both ends, it would form a parsable regex literal. For example, for new RegExp("/"), the source is \\/, because if it generates /, the resulting literal becomes ///, which is a line comment. Similarly, all line terminators will be escaped because line terminator characters would break up the regex literal. There's no requirement for other characters, as long as the result is parsable. For empty regular expressions, the string (?:) is returned.

Examples

Using source

js
const regex = /fooBar/gi;

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

Empty regular expressions and escaping

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

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

Specifications

Browser compatibility

Desktop Mobile Server
Chrome Edge Firefox Opera Safari Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet WebView Android Deno Node.js
source 1 12 1 5 1 18 4 10.1 1 1.0 4.4 1.0 0.10.0
empty_regex_string 6 12 38 15 5 18 38 14 4.2 1.0 ≤37 1.0 0.10.0
escaping 73 12 38 60 6 73 38 52 6 11.0 73 1.0 12.0.0
prototype_accessor 48 12 41 35 1.3 48 41 35 1 5.0 48 1.0 6.0.0

See also

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https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/source