Javascript array concatenation

Question

I have three variables a, b and c. I have to insert these into an array called arr. On calling function click, these variables should get pushed into arr array. eg. if i call click with arg 1,2 & 3 then array should be [1,2,3], now when I will pass the args 6,7 then the array should be [1,2,3,6,7]. In the code below, I tried to use concat method to get the desired result but i was unsuccessful.Is there any way around this?

function click(a,b,c){

    var A=a;
    var B=b;
    var C=c;

    var arr=[]
    var newArr=[A,B,C]
    arr.concat(newArr);
    console.log(arr);

}

click(10,11,12);
click(12,13,14);

you should declare the variable 'arr' outside the function click — Udit Kumawat
– Udit Kumawat, Commented Mar 22, 2018 at 4:54
you can use arr.push(newArr); Its another way to insert into an array. — Alauddin Ahmed
– Alauddin Ahmed, Commented Mar 22, 2018 at 4:56
@AlauddinAhmed i am getting [ [ 10, 11, 12 ], [ 12, 13, 14 ] ] ... not [10,11,12,12,13,14] :( — AConsumer
– AConsumer, Commented Mar 22, 2018 at 4:58
you can do arr.push(a, b, c) also, you dont need to assign them to another variable or array. — Alauddin Ahmed
– Alauddin Ahmed, Commented Mar 22, 2018 at 5:01

Herohtar · Accepted Answer · 2018-03-22 05:00:56Z

3

Declare a global array outside of the function and then after push values into it.

var arr = [];
function click(a,b,c){
    arr.push(a, b, c)
}

click(10,11,12);
click(12,13,14);

console.log(arr);

edited Mar 22, 2018 at 5:00

Herohtar

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answered Mar 22, 2018 at 4:55

Sagar Jajoriya

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Comments

Sai Kishore · Accepted Answer · 2018-03-22 04:57:03Z

3

The problem with your code is that, you are concatenating to the array but not considering the return value.

arr = arr.concat(newArr);

Then declare the array global to hold the values for every click.

answered Mar 22, 2018 at 4:57

Sai Kishore

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hungersoft · Accepted Answer · 2018-03-22 04:57:29Z

1

function click(arr, a, b, c){
    arr.push(a, b, c);
    console.log(arr);
}

var arr = [];
click(arr, 10, 11, 12);
click(arr, 12, 13, 14);

answered Mar 22, 2018 at 4:57

hungersoft

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guijob · Accepted Answer · 2018-03-22 05:05:38Z

1

If you don't want your arr outside your function, another approach is storing your arr inside click scope then call it anywhere (it doesn't pollute your global scope):

    let click = (function (arr) {
       return function (a,b,c) {
    
        var A=a;
        var B=b;
        var C=c;
    
        var newArr=[A,B,C]
        arr = arr.concat(newArr);
        console.log(arr);
      }
    })([])

    click(10,11,12);
    click(12,13,14);

edited Mar 22, 2018 at 5:05

answered Mar 22, 2018 at 4:59

guijob

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Comments

Vasyl Moskalov · Accepted Answer · 2018-03-22 04:58:54Z

0

First of all. You should either define arr outside your function or pass arr into function as a parameter. Second one. Function concat returns concatenated arrays and left original arrays unchanged. So you need something like arr=arr.concat(newArr)

answered Mar 22, 2018 at 4:58

Vasyl Moskalov

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Comments

Arman Charan · Accepted Answer · 2018-03-22 05:09:35Z

0

Destructuring assignment can be used to functionally concatenate variables with arrays.

See below for a practical example.

// Input.
const input = [1, 2, 3]

// Click.
const click = (array, ...arguments) => [...array, ...arguments]

// Output.
const output = click(input, 4, 5, 6)

// Proof.
console.log(output)

answered Mar 22, 2018 at 5:09

Arman Charan

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user1615664 · Accepted Answer · 2018-03-22 08:28:28Z

0

Your Problem here is that the concat function returns a new array instance with the elements: Check Here

    function click(a,b,c){

        var A=a;
        var B=b;
        var C=c;

        var arr=[]
        var newArr=[A,B,C]
        arr = arr.concat(newArr);
        // concat does not change the ref itself
        console.log(arr);

    }

click(10,11,12);
click(12,13,14);

edited Mar 22, 2018 at 8:28

answered Mar 22, 2018 at 4:59

user1615664

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