Function defineToken

Define a custom token that can be used in conjunction with other tokens. For a detailed guide on custom tokens, please read https://github.com/hlysine/readable-regexp#custom-tokens

Notes:

• TypeScript users should extend the RegExpToken interface to add their own custom tokens before calling this function.
• The token name must be a valid JavaScript identifier.
• The token name must not conflict with any existing properties of RegExpToken.
• All custom tokens should be defined before any tokens are used to build regular expressions.

Example

Create a constant token

Extend the RegExpToken interface to add a new token:

import { RegExpToken } from 'readable-regexp';

declare module 'readable-regexp' {
  interface RegExpToken {
    severity: RegExpToken;
  }
}
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Implement the custom token:

const severity = defineToken('severity', {
  constant(this: RegExpToken) {
    return this.oneOf`error` `warning` `info` `debug`;
  },
});
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Use the custom token:

// Referencing the token returned by the defineToken function
console.log(severity.toString()); // (?:error|warning|info|debug)

// Referencing the token in an expression
console.log(lineStart.severity.lineEnd.toString()); // ^(?:error|warning|info|debug)$
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