# spread operator(... array) + push function in Array javascript

**URL:** <https://forum.kirupa.com/t/spread-operator-array-push-function-in-array-javascript/643063>\
**Category:** programming\
**Created:** [June 2, 2020, 7:19pm UTC](https://forum.kirupa.com/t/spread-operator-array-push-function-in-array-javascript/643063 "2020-06-02T19:19:44Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Umair\_Ashraf](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/umair_ashraf/32/11705_2.png) [@Umair\_Ashraf](https://forum.kirupa.com/u/Umair_Ashraf)\
**Post date:** [June 2, 2020, 7:19pm UTC](https://forum.kirupa.com/t/spread-operator-array-push-function-in-array-javascript/643063/1 "2020-06-02T19:19:44Z")

</div>

hi guys,

I am a bit confused with the two below queries, really tankful if someone can clarify my concepts. 🙂

Query 1:  
when using spread operator in a function it de-structure and passes it as arguments , like

> let a = [1,2,3];  
> function x (…a) ;  
> it will be like function x(1,2,3) (1,2,3 passed as an argument here and not array anymore)

but one place i came across that after passing the array as spread operator we still can access indivisual items like

> a[0]=1, a[1]=2…

it confuses me as i though once it is passed in the function as array it is no more array and it elelemts will be passed as simple an argument.

Query 2:  
The below code works file, but at array1 =[s1,s2], i first tried to do like below,

> array1=array1.push(s1)  
> array1=array1.push(s2)

but this return TypeError: array1.push is not a function, not sure whats the reason that we cant push the contents of s1 and s2 variables indivisually…

> function sides(literals, …expressions) {
> 
> ```
> var array1=[]
> 
> ```
> 
> var area = expressions[0];  
> var perimeter = expressions[1];
> 
> var s1=(perimeter+Math.sqrt(perimeter_perimeter-16_area))/4;
> 
> var s2=(perimeter-Math.sqrt(perimeter_perimeter-16_area))/4;
> 
> array1 =[s1,s2]  
> return array1.sort();
> 
> }

---

<div class="post-metadata">

**Author:** ![senocular](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/senocular/32/7217_2.png) [@senocular](https://forum.kirupa.com/u/senocular)\
**Post date:** [June 2, 2020, 7:51pm UTC](https://forum.kirupa.com/t/spread-operator-array-push-function-in-array-javascript/643063/2 "2020-06-02T19:51:50Z")

</div>

You might be confusing array spread with rest parameters. Spread spreads out arrays and other iterables to individual values whereas rest parameters pulls in multiple parameters into a single array (a lot like the `arguments` object). Both use `...`.

```javascript
// spread
let nums = [1, 2, 3];
function x (one, two, three) {
    console.log(one);
    console.log(two);
    console.log(three);
}
x(...nums); // spreads out
/* logs:
1
2
3
*/

```

```javascript
// rest
let a = 1;
let b = 2;
let c = 3;
function x (...values) { // pulls together
    console.log(values);
}
x(a, b, c);
/* logs:
[1, 2, 3]
*/

```

```javascript
// both spread and rest
let nums = [1, 2, 3];
function x (...values) { // pulls together
    console.log(values);
}
x(...nums); // spreads out
/* logs:
[1, 2, 3]
*/

```