chainList (array) is populated (in moltab.js) from header COMPND in getChains()
COMPND obtained with
	var rawCompnd = jgetfi("compnd")
	jgetfi uses jmolGetPropertyAsString("fileInfo", "compnd")

COMPND lists sequence-identical chains in the same line.
See "chain names" in moltab.js.
For 1d66, chainList is D,E,AB

useLowerCaseChains is set in moltab.js

moltab.js also sets chainCount and distinctChainCount

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EndsChain (array) has one chain per element. For 1d66: D,E,A,B.
It is set from chainList in getChainEnds() in modeldat.js 

NOTE debugEnds! in modeldat.js

When there is no COMPND, chainList and EndsChain have length 0.
Then, getChainEnds (modeldat.js) populates EndsChain with jmolScriptEcho("show chains");

show chain messages a list of one chain name per line.

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chain type: moltab.js chainTypeFromName(chainName)

chainLengths[] are obtained from SEQRES in moltab.js (format "D 66").
If there are no SEQRES, chainLengths.length == 0.
In this case, "show chains" is used to get a list of chains in getChainEnds().