title: ParameterParser
modifier: colmbritton
created: 20110211110654
modified: 20110221143137
tags: features
creator: psd

The ParameterParser is used in several places in TiddlyWiki:
* to process the StartupParameters after the '#' in a TiddlyWiki URL
* to process the DefaultTiddlers list
* to process the parameters to Macros
* to process tag lists when editing a tiddler
It supports a list of parameters each of the form "name:value". For example:
{{{
name:John   location:"Isle of Wight"   [[dietary needs]]:none   really:'yes, really'
}}}
Names and values that need to contain spaces may be quoted with single- or double-quotes or double-square brackets. The parser is generally tolerant of additional spaces.

When processing macro parameters, names and values may also be quoted with double-braces which causes them to be evaluated as a [[JavaScript|http://en.wikipedia.org/wiki/JavaScript]] expression. For example:
{{{
title:{{window.title}}
}}}

The ParameterParser will cope with either the name or the value being omitted, and will substitute a specified default. This is how the StartupParameters work; the default parameter name is specified as 'open'.