Read from xlsx in javascript

@pinar, you will not be able to import Python libraries in the JS code, so you will need a different solution. The easiest option would be to use the PsychoJS trialHandler to load your excel sheet. E.g.,

trials = new TrialHandler({
		psychoJS: psychoJS,
		nReps: 1, method: TrialHandler.Method.RANDOM,
		extraInfo: expInfo, originPath: undefined,
		trialList: 'conditions.xlsx',
		seed: undefined, name: 'trials'
	});

trialList = trials.getTrialList()

This will return a list of JS objects (equivalent a list of Python dicts) and you can iterate through the list to get the column values. E.g.,

trialList[0]['myColumnHeader']  // row 1
trialList[1]['myColumnHeader']  // row 2