Editing Module:Japanese calendar/doc (section)

=== From another Lua module ===
First of all, the era class must be loaded, like this:

* <code lang="lua">local era = require( 'Module:Japanese calendar' ).era</code>

Once the class is loaded, you can make a new era object using <code>era:new()</code>: 

* <code lang="lua>local myEra = era:new{ year = ''year'', era = ''article name or kanji'' }</code>

Either <code>''year''</code> or <code>''era''</code> must be specified. It is also possible to use an <code>index</code> field, corresponding to the index of [[Module:Japanese calendar/data]], but this is for internal use only and will change as new eras are added.

==== Properties ====
Era objects have a number of properties. Their values might be <code>nil</code> if the module did not have enough information to process them, or the values could be <code>false</code> if they correspond to an invalid era. You can specify properties with the dot syntax:

* <code lang="lua">local article = myEra.article</code>

The properties are as follows:

* <code>gregorianYear</code>: the year in the [[Gregorian calendar]]. Same as the input year.
* <code>startYear</code>: the first year of the specified era.
* <code>endYear</code>: the last year of the specified era.
* <code>eraYear</code>: the year of the specified era, without the era name.
* <code>eraYearKanji</code>: a string representing the era year in [[kanji]]. The first year of an era is changed to the kanji 元, and the others are changed to [[Halfwidth and fullwidth forms|full-width]] numbers. Note: even though the output may often look like a number, it will always be a string value.
* <code>article</code>: the Wikipedia article for the era, unlinked.
* <code>label</code>: the name of the era. Same as <code>article</code> unless the article title is [[WP:DAB|disambiguated]].
* <code>kanji</code>: the name of the era in kanji.

==== Methods ====
Era objects have three methods. Methods can be specified with the colon syntax:

* <code lang="lua">local nextEra = myEra:getNextEra()</code>

The methods are as follows:
* <code lang="lua">era:getNextEra()</code> - gets the era object for the next era. Returns <code>nil</code> if it doesn't exist.
* <code lang="lua">era:getPreviousEra()</code> - gets the era object for the previous era. Returns <code>nil</code> if it doesn't exist.
* <code lang="lua">era:getOldEra()</code> - gets the era object for the "old" era. This is the same as the current era object unless eraYear equals 1. If eraYear equals 1 then this returns the era object for the previous era. If the module could not find a valid previous era object then the current era object is returned.

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