Symbol.match

The Symbol.match static data property represents the well-known symbol @@match. The String.prototype.match() method looks up this symbol on its first argument for the method used to match an input string against the current object. This symbol is also used to determine if an object should be treated as a regex.

For more information, see RegExp.prototype[@@match]() and String.prototype.match().

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Value

The well-known symbol @@match.

Property attributes of Symbol.match
Writable no
Enumerable no
Configurable no

Description

This function is also used to identify if objects have the behavior of regular expressions. For example, the methods String.prototype.startsWith(), String.prototype.endsWith() and String.prototype.includes(), check if their first argument is a regular expression and will throw a TypeError if they are. Now, if the match symbol is set to false (or a Falsy value except undefined), it indicates that the object is not intended to be used as a regular expression object.

Examples

Marking a RegExp as not a regex

The following code will throw a TypeError:

"/bar/".startsWith(/bar/);

// Throws TypeError, as /bar/ is a regular expression
// and Symbol.match is not modified.

However, if you set Symbol.match to false, the object will be considered as not a regular expression object. The methods startsWith and endsWith won't throw a TypeError as a consequence.

const re = /foo/;
re[Symbol.match] = false;
"/foo/".startsWith(re); // true
"/baz/".endsWith(re); // false

Specifications

Specification
ECMAScript Language Specification
# sec-symbol.match

Browser compatibility

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See also