How to pass values for Data Change Type in custom service

I am trying to use AddPropertyDefinition in a service where I am passing values like "ALWAYS" or "Always", "VALUE" or "value" etc it is showing error as shown:-

[message: Execution error in service script [PropertyCreationAndValueUpdation] :: Invalid Data Change Type : [Value]]

Could anyone let me the exact way of updating this part

Code is as:-

var params = {
defaultValue: undefined /* STRING */,
remoteBindingAspects: undefined /* JSON */,
description: undefined /* STRING */,
readOnly: false /* BOOLEAN */,
remote: undefined /* BOOLEAN */,
type: propertyType.toUpperCase() /* BASETYPENAME */,
remotePropertyName: undefined /* STRING */,
timeout: undefined /* INTEGER */,
pushType: undefined /* STRING */,
dataChangeThreshold: undefined /* NUMBER */,
logged: true /* BOOLEAN */,
name: propertyName /* STRING */,
pushThreshold: undefined /* NUMBER */,
dataChangeType: undefined /* STRING */,   ----------> This part is showing error when passing above values.
category: undefined /* STRING */,
persistent: true /* BOOLEAN */,
dataShape: undefined /* DATASHAPENAME */
};

me.AddPropertyDefinition(params);