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I am trying to implement lodash _.difference(array, [values]) using .filter() method


By : marius1111
Date : October 16 2020, 08:10 AM
seems to work fine The method/function needs to return an array that has elements in the 1st array that are not present in the second array. , You can use Array.filter() with Array.includes():
code :
const arr1 = [1,2,3];
const arr2 = [2,3,4,5,6];

const difference = (a, b) => a.filter(item => !b.includes(item));
  
const result = difference(arr1, arr2);

console.log(result);


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lodash Filter collection using array of values


By : SerpentSolide
Date : March 29 2020, 07:55 AM
will be helpful for those in need If you're going to use this sort of pattern a lot, you could create a mixin like the following, though, it isn't doing anything fundementally different than your original code. It just makes it more developer friendly.
code :
_.mixin({
  'findByValues': function(collection, property, values) {
    return _.filter(collection, function(item) {
      return _.contains(values, item[property]);
    });
  }
});
var collections = [
    {id: 1, name: 'xyz'}, 
    {id: 2,  name: 'ds'},
    {id: 3,  name: 'rtrt'},
    {id: 4,  name: 'nhf'},
    {id: 5,  name: 'qwe'}
];

var filtered = _.findByValues(collections, "id", [1,3,4]);
_(collections)
  .keyBy('id') // or .indexBy() if using lodash 3.x
  .at(ids)
  .value();

LoDash challenges, I have an array of objects I need to filter, for an array of values


By : user3137134
Date : March 29 2020, 07:55 AM
With these it helps I have the following array of objects that I need to filter by _id using an array of _id values. , This is the fastest way I know how to do it using LoDash:
code :
var objects = [{
    _account: "YzzrzBrO9OSzo6BXwAvVuL5dmMKMqkhOoEqeo",
    _id:      "055z5gzVyVfzlBnEOqYvcoLL1ZgOWJhkrWMkv2"
}, {
    _account: "YzzrzBrO9OSzo6BXwAvVuL5dmMKMqkhOoEqeo",
    _id:      "LvvrvyrOGOS2e5yE0Bdki45Y1ndVlgfoZ2zoOp"
}, {
    _account: "mjj9jp92z2fD1mLlpQYZI1gAd4q4LwTKmBNLz",
    _id:      "rEEwENwnznCQvkm61wRziKlMRPqaYztnR4vn61"
}, {
    _account: "AaaraZrLqLfzRYoAPlb6ujPELWVW4dTK4eJWj",
    _id:      "944r40rPgPU2nXqzMYolS5nyo6Eo9OuqrlDkB"
}, {
    _account: "AaaraZrLqLfzRYoAPlb6ujPELWVW4dTK4eJWj",
    _id:      "rEEwENwnznCQvkm61wZ9uey62Pjy5YTqgYGDK"
}];

var id_values = [
    "rEEwENwnznCQvkm61wZ9uey62Pjy5YTqgYGDK",
    "944r40rPgPU2nXqzMYolS5nyo6Eo9OuqrlDkB",
    "rEEwENwnznCQvkm61wRziKlMRPqaYztnR4vn61"
];

var index  = index_of_array(id_values);

var result = _.reject(objects, function (object) {
    return index[object._id] || false;
});

console.log(result);
<script src="http://cdn.jsdelivr.net/lodash/2.1.0/lodash.compat.js"></script>

<script>
/*
  Creates an index of an array of keys. Allows you to check whether the array
  has a specific key in O(1) time (as compared to O(n) time using indexOf). It
  takes O(n) time to create the index where n is the length of the array.

  e.g.

  var keys  = [1,2,3];
  var index = index_of_array(keys);     //         O(n) time
  console.log(index[1] || false);       // true  - O(1) time
  console.log(index[4] || false);       // false - O(1) time
  console.log(keys.indexOf(1) >= 0);    // true  - O(n) time
  console.log(keys.indexOf(4) >= 0);    // false - O(n) time
*/

function index_of_array(array) {
    var length = array.length
      , result = {}
      , index  = 0;

    while (index < length)
        result[array[index++]] = true;
    return result;
}
</script>

How can I filter a nested object with an array of values using lodash?


By : Mahajan
Date : March 29 2020, 07:55 AM
wish help you to fix your issue You can use _.filter for the main array you are trying to retrieve as the end result and then use _.chain with _.map and _.intersection to filter the internal the objects array.
Something like the code bellow should suffice, although it is not pretty.
code :
var self = this;

_.filter(jobs, function(job) { 

  return _.chain(job.industry)
    .map('name')
    .intersection(self.jobchoices)
    .size()
    .gt(0)
    .value() 
})

lodash: Filter collection using array of values


By : Vanlade
Date : March 29 2020, 07:55 AM
This might help you I found this solution: , If by all values you mean the objects, then
code :
const values = collections.filter(e => ['somename1', 'somename2'].includes(e.name))
const descriptions = values.map(e => e.description)

How to emulate lodash .find method in a Express app with Array.prototype.filter method


By : Brenda Pabon
Date : March 29 2020, 07:55 AM
wish helps you
The FIND method gets the very first element that meets the expression as TRUE. FILTER will return any item that meets the expression as TRUE.
code :
app.get('/lions/:id', function(req, res){
  var lion = lions.filter(function(id){ 
    return id === req.params.id;
  });
  res.json(lion || {});
});
var numbers = [9,3,5,0,-1];

var result = numbers.filter(function(num){
  return num;
});

// result => [9,3,5,-1]; zero is falsey.
// Filter does not return the actual number, only if the result is truthey.
// So returning something like **{id: req.params.id}** is always truthy
// because an object is true !!{} === true; => TRUE.
// Even if {id: undefined};
// Also, note that the filter function passed everything into the new array that was truthy,
// which is NOT what **FIND** does.
var lions = [{id: 2, name: "blue"}, {id: 4, name: "green"}, {id:8, name: "red"}, {id: 2, name: "yellow"}];


app.get('/lions/:id', function(req, res){
  res.json(lions[lions.map(ids).indexOf(req.params.id)] || {});
});

// Helper Functions

function ids(lion){
  return lion.id;
}
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