Get an object from array which contains a specific

问题:

I am trying to search through an array of objects using Underscore.js, but I can't seem to target the one I want.

console.log(_.findWhere(response.data, { TaskCategory: { TaskCategoryId: $routeParams.TaskCategory } }));

However, this is returning undefined $routeParams.TaskCategory is equal to 301

This is an example of the objects inside the array I am searching. This data is represented by data.response

[{
    "TaskCategory": {
        "TaskCategoryId": 201,
        "TaskName": "TaskName"
    },
    "TaskCount": 1,
    "Tasks": [{
        "EventTypeId": 201,
        "EventName": "Event Driver",
        "EventDate": "0001-01-01T00:00:00",
        "EventId": "00000000-0000-0000-0000-000000000000",
    }]
},
{
    "TaskCategory": {
        "TaskCategoryId": 301,
        "TaskName": "TaskName"
    },
    "TaskCount": 1,
    "Tasks": [{
        "EventTypeId": 201,
        "EventName": "Event Driver",
        "EventDate": "0001-01-01T00:00:00",
        "EventId": "00000000-0000-0000-0000-000000000000",
    }]
}]

So I want the second object in that array using the TaskCategory.TaskCategoryId, is it possible to get it using Underscore?

回答1:

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.

回答2:

The source of _.findWhere / _.where is as follows

_.where = function(obj, attrs, first) {
  if (_.isEmpty(attrs)) return first ? void 0 : [];
  return _[first ? 'find' : 'filter'](obj, function(value) {
    for (var key in attrs) {
      if (attrs[key] !== value[key]) return false;
    }
    return true;
  });
};

_.findWhere = function(obj, attrs) {
  return _.where(obj, attrs, true);
};

As you can see, it performs strict equality rather than deep equality. If you want a deep searching where, this would suffice (untested, unoptimized):

_.whereDeep = function(obj, attrs, first) {
  if (_.isEmpty(attrs)) return first ? void 0 : [];
  return _[first ? 'find' : 'filter'](obj, function(value) {
    for (var key in attrs) {
      if (attrs[key] !== value[key] || !(_.isObject(attrs[key]) && _.whereDeep([value[key]], attrs[key], true))) return false;
    }
    return true;
  });
};

_.findWhereDeep = function(obj, attrs) {
  return _.whereDeep(obj, attrs, true);
};

And you would be able to use your code, almost unchanged

_.findWhereDeep(response.data, { TaskCategory: { TaskCategoryId: $routeParams.TaskCategory } });