Get an object from array which contains a specific value

Use _.find instead of findWhere:

console.log(_.find(response.data, function(item) {
    return item.TaskCategory.TaskCategoryId == $routeParams.TaskCategory; 
}));

They are similar, but findWhere is designed for special cases where you want to match key-value pairs (not useful in your scenario as it involves nested objects). Find is more general-use, because it lets you provide a function as the predicate.