When push a data into array is pushing in just one index

Question

Hi there guys I am new in this but I have a array in my localstorage I get that array I save in old empty array, and I make a petition to the ajax and I try push the new data into my old array

$.getJSON(setUrl(pagination, page), function (response) {
            var old = []; 
            old = JSON.parse(localStorage.getItem('msg'));
            old.push(response.DATA);
            console.log(old);
});

but the result I getting is some like this

I put all my new array inside a index of my old array what am I doing wrong ? can some one help me

This happens when response.DATA is an array. This is behaving as expected. If you want to add each item individually, iterate over them. — Bucket, Nov 15 '18 at 16:16
possible duplicate of https://stackoverflow.com/questions/1374126/how-to-extend-an-existing-javascript-array-with-another-array-without-creating — Tanmay, Nov 15 '18 at 16:33

Alexander Staroselsky · Answer 1 · 2018-11-15T16:28:13.623

1

Use Array.ptototype.concat() instead to merge the arrays. Array.prototype.concat():

The concat() method is used to merge two or more arrays. This method does not change the existing arrays, but instead returns a new array.

$.getJSON(setUrl(pagination, page), function (response) {
  var old = []; 
  old = JSON.parse(localStorage.getItem('msg'));
  old = old.concat(response.DATA);
  console.log(old);
});

var old = [
  { id: 1 },
  { id: 2 }
];

console.log('old: ', old);

var json = [
  { id: 3 },
  { id: 4 }
];

old = old.concat(json);

console.log('merged: ', old);

Hopefully that helps!

edited Nov 15 '18 at 16:28

answered Nov 15 '18 at 16:16

Alexander Staroselsky

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I use concat before but the element return is the same array – Alfredo Izquierdo Nov 15 '18 at 16:19
I try save each element as a new element in the old array – Alfredo Izquierdo Nov 15 '18 at 16:20
You are right, I missed a key portion in my answer. `concat()` returns a new array so it would need to be saved to a variable. Updated the answer. – Alexander Staroselsky Nov 15 '18 at 16:21
@AlfredoIzquierdo You can reassign the value of `old` if the goal is to specifically use `old` again in the method or elsewhere. I've updated the answer to reflect that. – Alexander Staroselsky Nov 15 '18 at 16:40

score 1 · Answer 2 · answered Nov 15 '18 at 16:20

You have to use concat but remember....

The concat() method is used to merge two or more arrays. This method does not change the existing arrays, but instead returns a new array. _source

$.getJSON(setUrl(pagination, page), function (response) {
        var old = []; 
        old = JSON.parse(localStorage.getItem('msg'));
        var combined = old.concat(response.DATA);
        console.log(combined);
});

When push a data into array is pushing in just one index

2 Answers2