created: 20210203150855206
modified: 20210203150855206
title: ParserSubclassingMechanism

!! Introduction

The wikitext parser subclassing mechanism makes it possible for custom parsers to use the wiki text parsing engine, but to customise the rules that are used.

!! Example

Here is an example of a subclass of the checkbox widget that adds logging to the event handler:

```js
(function(){

/*jslint node: true, browser: true */
/*global $tw: false */
"use strict";

var WikiParser = require("$:/core/modules/parsers/wikiparser/wikiparser.js")["text/vnd.tiddlywiki"],
	HtmlParser = $tw.modules.createClassFromModule(require("$:/core/modules/parsers/wikiparser/rules/html.js"),$tw.WikiRuleBase),
	EntityParser = $tw.modules.createClassFromModule(require("$:/core/modules/parsers/wikiparser/rules/entity.js"),$tw.WikiRuleBase);

var MyCustomWikiParser = function(type,text,options) {
	var parser = new WikiParser(type,text,$tw.utils.extend({},options,{
		// Force the parser to parse in inline mode
		parseAsInline: true,
		// Specify which rules will be used
		rules: {
			pragma: [],
			block: [],
			inline: [HtmlParser,EntityParser]
		}
	}));
	this.tree = parser.tree;
	this.prototype = parser.prototype;
};

exports["text/vnd.my-custom-type"] = MyCustomWikiParser;

})();
```