How to extend array object by another array using Underscore.JS [duplicate]

Question

I have below list objects:

Object 1:

[{
    empId: 1, 
    name: AAA, 
    schoolId: 1
}, {
    empId: 2, 
    name: BBB, 
    schoolId: 2
}]

And Object 2:

[{
    schoolId: 1, 
    schoolName: SchoolA
}, {
    schoolId: 2, 
    schoolName: SchoolB
}]

In both objects Object1 and Object2, SchoolId is common field. Which can be accessed as a mapping field.

Now I using _.extend method of UnderscoreJS I want to achieve below object:

Output:

[{
    empId: 1, 
    name: AAA, 
    schoolId: 1, 
    school: SchoolA
}, {
    empId: 2, 
    name: BBB, 
    schoolId: 2, 
    school: SchoolB
}]

Can you please suggest how can I achieve this ? Thanks

Ori Drori · Accepted Answer · 2017-09-26 11:09:08Z

1

Create an index (arr1Index) by schoolId of 1st array using _.indexBy(), then _.map() the 2nd array, and create a new object that extends the current object, with an object with the same schoolId from the arr1Index:

var arr1 = [{"empId":1,"name":"AAA","schoolId":1},{"empId":2,"name":"BBB","schoolId":2}];

var arr2 = [{"schoolId":1,"schoolName":"SchoolA"},{"schoolId":2,"schoolName":"SchoolB"}];

var arr1Index = _.indexBy(arr1, 'schoolId');

var result = _.map(arr2, function(o) {
  return _.extend({}, o, arr1Index[o.schoolId]);
});

console.log(result);

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answered Sep 26, 2017 at 11:09

Ori Drori

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Comments

Thusitha · Accepted Answer · 2017-09-26 11:18:44Z

0

You can combine each and findWhere as below.

var d1 = [{
  empId: 1,
  name: "AAA",
  schoolId: 1
}, {
  empId: 2,
  name: "BBB",
  schoolId: 2
}];

var d2 = [{
  schoolId: 1,
  schoolName: "SchoolA"
}, {
  schoolId: 2,
  schoolName: "SchoolB"
}];

var output = _.each(d1, function(obj) {
  obj.school = _.findWhere(d2, {
    schoolId: obj.schoolId
  }).schoolName;
});

console.log(output);

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answered Sep 26, 2017 at 11:18

Thusitha

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Comments

Satendra · Accepted Answer · 2017-09-26 11:23:21Z

0

You can use _extend and _find

var arr1 = [{"empId":1,"name":"AAA","schoolId":1},{"empId":2,"name":"BBB","schoolId":2}];

var arr2 = [{"schoolId":1,"schoolName":"SchoolA"},{"schoolId":2,"schoolName":"SchoolB"}];


var output = _.each(arr1, function(a1) {
    _.extend(a1, _.find(arr2, function(a2) {
        return a2.schoolId == a1.schoolId; 
    }))
});

console.log(output)

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answered Sep 26, 2017 at 11:23

Satendra

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Comments

Mikhail Shabrikov · Accepted Answer · 2017-09-26 11:46:04Z

You can do it this way (Note: This solution expects that we have two arrays with the same length and the N-th element of the first array should be extended with the N-th element of the second array etc.):

var arrayOne = [{
    empId: 1, 
    name: 'AAA', 
    schoolId: 1
}, {
    empId: 2, 
    name: 'BBB', 
    schoolId: 2
}];

var arrayTwo = [{
    schoolId: 1, 
    schoolName: 'SchoolA'
}, {
    schoolId: 2, 
    schoolName: 'SchoolB'
}];

var result = _.map(arrayOne, function(value, index) {
	return _.extend({}, value, arrayTwo[index])
})

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>

And one addition remark - with Lodash, this problem solves more concisely:

_.zipWith(arrayOne, arrayTwo, _.assign) // ==> returns what you need

Example with Lodash

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