问将实体编辑回原来的值时，hasChanges()

EN

em.entityChanged.subscribe(function(changeArgs) {
    var action = changeArgs.entityAction;
    var entity = changeArgs.entity;
    var ovs = entity.entityAspect.originalValues
    if (action == breeze.EntityAction.PropertyChange) {
        for (var prop in ovs) {
            if (prop in entity) {
                 // As soon as a non-matching property is discovered,
                 // then 'Modified' is the appropriate state, so exit
                 if (entity[prop] !== ovs[prop]) return;
            }
        }
        // all the properties are the same.  mark it unchanged
        entity.entityAspect.setUnchanged();
    } 
});