Compare object with an array

Question

I've an object and the array as shown below and I wanted to remove all the properties of the object except those listed in the array. Can someone help me with a good lodash function to do this.

object : {A:1,B:2,C:3,D:4} 
array: [{type:B,value:xyz,order:1},{type:D,value:abc,order:0}]

I want the object to be {B:2,D:4} after the operation

@Kinduser, thanks for the response. I know how to do it in pure js, but I'm looking for a solution using lodash as we've been using that in our project and wanted to learn the same. — Ajay Srikanth
– Ajay Srikanth, Commented Mar 13, 2017 at 21:07
do you want to mutate the object, or just filter it, or does it not matter? — orion
– orion, Commented Mar 13, 2017 at 21:11
@orion, I want to mutate the object, so that the object contains only the fields that are present in array. — Ajay Srikanth
– Ajay Srikanth, Commented Mar 13, 2017 at 21:14

ibrahim mahrir · Accepted Answer · 2017-03-13 22:57:43Z

3

Use _.pick like this:

var result = _.pick(object, array);

var object = {
  A: 1,
  B: 2,
  C: 3,
  D: 4
};

var array = ["B", "D"];

var result = _.pick(object, array);

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

EDIT:

You should first use _.map to get the keys and then use _.pick like this:

var result = _.pick(object, _.map(array, function(e) {
  return e.type;
}));

or using arrow functions like this:

var result = _.pick(object, _.map(array, e => e.type));

or even shorter using the iteratee argument like this:

var result = _.pick(object, _.map(array, "type"));

var object = {
  A: 1,
  B: 2,
  C: 3,
  D: 4
};

var array = [{type: "B", value: "xyz", order: 1}, {type: "D", value: "abc", order: 0}];

var result = _.pick(object, _.map(array, "type"));

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

edited Mar 13, 2017 at 22:57

answered Mar 13, 2017 at 21:13

ibrahim mahrir

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6 Comments

Ajay Srikanth Over a year ago

hi, ibrahim thanks for the answer. First of all my apologies, I missed the crucial part of my array at least I believe which I've modified now. I realized about that mistake in my question only after looking at your answer as I've already read about pick before posting my question.

ibrahim mahrir Over a year ago

@AjaySrikanth see the EDIT section above!

Ajay Srikanth Over a year ago

Thanks ibrahim. This is what I wanted.

ryeballar Over a year ago

you can shorten this with var result = _.pick(object, _.map(array, 'type'));

ibrahim mahrir Over a year ago

@ryeballar yeah even clearer, didn't know you can do that so thanks!

|

guest271314 · Accepted Answer · 2017-03-13 21:42:24Z

2

You can use Object.assign(), Array.prototype.map() , spread element, computed property, to assign result of filtering type properties to object

var object = {A:1,B:2,C:3,D:4} 
var array = [{type:"B",value:"xyz",order:1},{type:"D",value:"abc",order:0}];
object = Object.assign({}, ...array.map(({type}) => ({[type]:object[type]})));

console.log(object);

answered Mar 13, 2017 at 21:42

guest271314

1

2 Comments

Ajay Srikanth Over a year ago

what is the ... in Object.assign() ? Could you please explain that syntax. I've just started as full time js developer. I'm having trouble understanding few syntax here and there.

guest271314 Over a year ago

@AjaySrikanth See What is SpreadElement in ECMAScript documentation? Is it the same as Spread operator at MDN?

Matt D. Webb · Accepted Answer · 2017-03-14 09:32:36Z

0

You can use _.pick along with _.map to achieve this:

let obj = { A:1, B:2, C:3, D:4 };
let arr = [{ type:'B', value:'xyz', order:1 },{ type:'D', value:'abc', order:0 }];

let output = _.pick(obj, _.map(arr, 'type'));

console.log(output); // { B:2, D: 4 }

Example: JsFiddle

Lodash Docs:

_.map(): link

_.pick(): link

edited Mar 14, 2017 at 9:32

answered Mar 13, 2017 at 21:35

Matt D. Webb

3,3324 gold badges32 silver badges53 bronze badges

2 Comments

ibrahim mahrir Over a year ago

Check the desired output again!

Matt D. Webb Over a year ago

@ibrahimmahrir Ah pants! :-)

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