A function that makes sure an options object has a certain set of expected properties. If properties are missing or of the wrong type, they are set to the default values defined in propInfoDict.

prepareOptions.js

// propInfoDict should have prop names as the keys, then arrays 
// as values that contain the expected type and the default value.
// options should be the options dictionary.

// Example:
// options = prepareOptions(options, {
// 	someDictionary: ['object', null],
// 	aFunction: ['function', function(datum) {
// 		return datum;
// 	}],
//  message: ['string', 'OHAY GUYS'],
//  count: ['number', 1000000]
// });

function prepareOptions(options, propInfoDict) {
  if (!options) {
    options = {};
  }
    
  for (var propName in propInfoDict) {
		var valid = optionIsValid(options, propName, 
			propInfoDict[propName][0]);
		if (!valid) {
			options[propName] = propInfoDict[propName][1];
		}
	}
  
  return options;
}

function optionIsValid(optionsDict, propName, expectedTypeName) {
  var valid = false;
	var value = optionsDict[propName];
	if (typeof value === expectedTypeName) {
		if (expectedTypeName === 'string') {
			if (value.length) {
				valid = true;
			}
		}
		else {
			valid = true;
		}
	}
  return valid;
}