How to remove an object from an array based on another array with Lodash?

Question

I am trying to edit an array of objects that I have based on another array.

For example, this is my array of objects:

var objs = [{ 
   attending: 0, user: '123' 
}, { 
   attending: 0, user: '456' 
}, { 
   attending: 0, user: '789' 
}];

And this is my array:

var arr = ['945', '456']

Since 456 exists within arr, I would like to remove that object from obj. Hence being the final result of:

var objs = [{ 
   attending: 0, user: '123' 
}, { 
   attending: 0, user: '789' 
}];

I have tried both omit and pullByAll yet had no luck:

var newObj = _.omit(obj, arr);
var newObj = _.pullAllBy(obj, arr, 'user');

What would be the best approach to this while using Lodash? I understand that creating a Javascript function for this would be quite simple, although my app requires this to be done quite often, so would be good to have a simple Lodash function that is accessible.

Why do you feel the need for using lodash? If performance is your concern, using vanilla js probably more transparent and easier to optimize. — lipp
– lipp, Commented May 30, 2016 at 7:08
How many elements (magnitude) are you expecting in arr and objs respectively? Do you "re-query" objs for every request or is it "global"? — lipp
– lipp, Commented May 30, 2016 at 7:17

atinder · Accepted Answer · 2016-05-30 07:32:12Z

2

You can use native js method to do that.

var newObj = objs.filter(function(obj) {
  return arr.indexOf(obj.user) != -1
});

if you are using ES6 its even more simple

var newObj = objs.filter(obj => arr.indexOf(obj.user) != -1);

There is this video which explains this concept very nicely.

answered May 30, 2016 at 7:32

atinder

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Comments

Andrew · Accepted Answer · 2018-11-13 17:09:33Z

2

As asked, here it is in lodash:

var newObj = _.filter(objs, function(obj) {
  return _.indexOf(arr, obj.user) !== -1;
});

We can debate plain js vs lodash till the cows come home, but 1) the question asks for lodash, and 2) if objs or arr are null, the plain js answers will throw an error.

answered Nov 13, 2018 at 17:09

Andrew

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Comments

lipp · Accepted Answer · 2016-05-30 07:00:48Z

1

With plain JS this would work:

var newObj = objs.filter(function(obj) {
   return arr.indexOf(obj.user) !== -1
})

answered May 30, 2016 at 7:00

lipp

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2 Comments

RobG Over a year ago

The OP says "…I would like to remove that object from obj.', Whereas filter creates a new array. Something like reduceRight might suit: objs.reduceRight(function(acc, v, i){if (acc.indexOf(v.user) != -1) objs.splice(i, 1); return acc}, arr). But still no lodash. :-(

lipp Over a year ago

Right. Thanks. Would be interesting to know the whole repetitive / performance critical sequence

Fizzix · Accepted Answer · 2016-05-30 07:02:35Z

0

I was able to solve this with a combination of both forEach() and remove()

_(obj).forEach(function(value) {
    _.remove(arr, {
        user: value
    });
});

answered May 30, 2016 at 7:02

Fizzix

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