push the contents of array into another array without looping

Question

Here's a simple piece of JavaScript where I want to add the contents of orders.foo and orders2.foo to a single-dimensional ordersArr.

let _ = require('underscore');

let ordersArr = [];
let orders = {
    foo: [
        {x: 1, b: 2},
        {y: 1, c: 3},
        {a: 2, d: 4}
    ]
}

ordersArr = _.map(orders.foo, order => order)

orders2 = {
        foo: [
                {x: 2, b: 3},
                {y: 5, c: 4},
                {a: 3, d: 6}
        ]
}


let tOrders = _.map(orders2.foo, order => order);
ordersArr.push(tOrders)

console.log(ordersArr);

The problem with this code is that push in this case creates a multi-dimensional array:

Output

[
  { x: 1, b: 2 },
  { y: 1, c: 3 },
  { a: 2, d: 4 },
  [ { x: 2, b: 3 }, { y: 5, c: 4 }, { a: 3, d: 6 } ]
]

How do I iterate the contents of orders.foo and orders2.foo and have their results as one single dimension array?

Leshawn Rice · Accepted Answer · 2021-10-21 21:15:00Z

8

You can spread the content of both arrays into the new array

const arr1 = [1,2,3];
const arr2 = [4,5,6];
const arr3 = [...arr1, ...arr2];
console.log(arr3);
// prints [1,2,3,4,5,6]

Spreading arr2 into arr1 also works.

arr1.push(...arr2);
console.log(arr1);
// prints [1,2,3,4,5,6]

So changing

ordersArr.push(tOrders)

to

ordersArr.push(...tOrders);

should work.

For a full answer:

let ordersArr = [];
let orders = {
    foo: [
        {x: 1, b: 2},
        {y: 1, c: 3},
        {a: 2, d: 4}
    ]
}

orders2 = {
        foo: [
                {x: 2, b: 3},
                {y: 5, c: 4},
                {a: 3, d: 6}
        ]
}

ordersArr.push(...orders.foo, ...orders2.foo);

edited Oct 21, 2021 at 21:15

answered Oct 21, 2021 at 20:58

Leshawn Rice

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Comments

Majed Badawi · Accepted Answer · 2021-10-21 21:28:32Z

Using underscore _.flatten:

const 
  orders = { foo: [ {x: 1, b: 2}, {y: 1, c: 3}, {a: 2, d: 4} ] },
  orders2 = { foo: [ {x: 2, b: 3}, {y: 5, c: 4}, {a: 3, d: 6} ] };
  
const ordersArr = _.flatten([orders.foo, orders2.foo]);

console.log(ordersArr);

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.2/underscore-min.js"></script>

Using javascript spread operator:

const 
  orders = { foo: [ {x: 1, b: 2}, {y: 1, c: 3}, {a: 2, d: 4} ] },
  orders2 = { foo: [ {x: 2, b: 3}, {y: 5, c: 4}, {a: 3, d: 6} ] };
  
const ordersArr = [...orders.foo, ...orders2.foo];

console.log(ordersArr);

Using javascript Array#concat:

const 
  orders = { foo: [ {x: 1, b: 2}, {y: 1, c: 3}, {a: 2, d: 4} ] },
  orders2 = { foo: [ {x: 2, b: 3}, {y: 5, c: 4}, {a: 3, d: 6} ] };
  
const ordersArr = orders.foo.concat(orders2.foo);

console.log(ordersArr);

Vrienden van Andries · Accepted Answer · 2021-10-21 21:31:04Z

4

The spread operator mentioned above is the best 2021 way to do it.

let ordersArr = [...orders.foo, ...orders2.foo];

answered Oct 21, 2021 at 21:31

Vrienden van Andries

1211 silver badge4 bronze badges

Comments

code_monk · Accepted Answer · 2021-10-21 21:09:57Z

2

Use Array.concat()

let orders1 = {
    foo: [
        {x: 1, b: 2},
        {y: 1, c: 3},
        {a: 2, d: 4}
    ]
};

let orders2 = {
    foo: [
        {x: 2, b: 3},
        {y: 5, c: 4},
        {a: 3, d: 6}
    ]
};

console.log( orders1.foo.concat(orders2.foo) );

answered Oct 21, 2021 at 21:09

code_monk

10.2k3 gold badges46 silver badges45 bronze badges

Comments

The fourth bird · Accepted Answer · 2021-10-21 21:56:54Z

You can use concat() to merge the arrays and create a single new array:

let tOrders = orders.foo.concat(orders2.foo);

let ordersArr = [];
let orders = {
    foo: [
        {x: 1, b: 2},
        {y: 1, c: 3},
        {a: 2, d: 4}
    ]
}

ordersArr = _.map(orders.foo, order => order)

orders2 = {
    foo: [
        {x: 2, b: 3},
        {y: 5, c: 4},
        {a: 3, d: 6}
    ]
}

let tOrders = orders.foo.concat(orders2.foo);
console.log(tOrders)

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.2/underscore-min.js"></script>

Another option using flat()

let ordersArr = [];
let orders = {
    foo: [
        {x: 1, b: 2},
        {y: 1, c: 3},
        {a: 2, d: 4}
    ]
}

orders2 = {
    foo: [
        {x: 2, b: 3},
        {y: 5, c: 4},
        {a: 3, d: 6}
    ]
}

let tOrders = [orders.foo, orders2.foo].flat();
console.log(tOrders)

Rukshan Jayasekara · Accepted Answer · 2021-10-21 21:18:28Z

Immutable merge of arrays

Creates a new array.

Merge using the spread operator

let orders = {
    foo: [
        {x: 1, b: 2},
        {y: 1, c: 3},
        {a: 2, d: 4}
    ]
}

let orders2 = {
    foo: [
        {x: 2, b: 3},
        {y: 5, c: 4},
        {a: 3, d: 6}
     ]
}

const mergeResult = [...orders.foo, ...orders2.foo];
console.log(mergeResult);

Merge using array.concat() method

let orders = {
    foo: [
        {x: 1, b: 2},
        {y: 1, c: 3},
        {a: 2, d: 4}
    ]
}

let orders2 = {
    foo: [
        {x: 2, b: 3},
        {y: 5, c: 4},
        {a: 3, d: 6}
     ]
}

const mergeResult = orders.foo.concat(orders2.foo);
console.log(mergeResult);

Mutable merge of arrays

Merge it into existing array.

Merge using array.push() method

let orders = {
    foo: [
        {x: 1, b: 2},
        {y: 1, c: 3},
        {a: 2, d: 4}
    ]
}

let orders2 = {
    foo: [
        {x: 2, b: 3},
        {y: 5, c: 4},
        {a: 3, d: 6}
     ]
}

orders.foo.push(...orders2.foo);
console.log(orders.foo);

Julian Gonggrijp · Accepted Answer · 2021-10-22 11:46:20Z

1

I'll add one more flavor to the list. You can create a shallow copy of an array using the built-in slice method, which has been with us for a very long time:

var ordersArr = orders.foo.slice();

Now you can add the contents of the other array using push and apply:

ordersArr.push.apply(ordersArr, orders2.foo);

Et voilá, ordersArr is now a one-dimensional array containing all elements of both orders.foo and orders2.foo. Works even in ES3!

For inspiration, you can find lots of nice little tricks like this in the Underscore source code.

answered Oct 22, 2021 at 11:46

Julian Gonggrijp

4,42521 silver badges44 bronze badges

Comments

mohammad mohammadi nodhe · Accepted Answer · 2021-10-21 21:03:34Z

0

i think this will work for you.

let tOrders = _.map(orders2.foo, order => order);
tOrders.foreach((element)=>{
ordersArr.push(element)
})
console.log(ordersArr);

answered Oct 21, 2021 at 21:03

mohammad mohammadi nodhe

2,2881 gold badge8 silver badges17 bronze badges

1 Comment

Leshawn Rice Over a year ago

The post title says without looping, but this answer will work

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