How to append something to an array?

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How do I append an object (such as a string or number) to an array in JavaScript?

javascriptarraysappend

Answers

answered 10 years ago jdecuyper #1

Use the push() function to append to an array:

// initialize array
var arr = [
    "Hi",
    "Hello",
    "Bonjour"
];

// append new value to the array
arr.push("Hola");

console.log(arr);

Will print

["Hi", "Hello", "Bonjour", "Hola"]

You can use the push() function to append more than one value to an array in a single call:

// initialize array
var arr = [ "Hi", "Hello", "Bonjour", "Hola" ];

// append multiple values to the array
arr.push("Salut", "Hey");

// display all values
for (var i = 0; i < arr.length; i++) {
    console.log(arr[i]);
}

Will print

Hi
Hello
Bonjour
Hola 
Salut
Hey

Update

If you want to add the items of one array to another array, you can use firstArray.concat(secondArray):

var arr = [
    "apple",
    "banana",
    "cherry"
];

arr = arr.concat([
    "dragonfruit",
    "elderberry",
    "fig"
]);

console.log(arr);

Will print

["apple", "banana", "cherry", "dragonfruit", "elderberry", "fig"]

answered 10 years ago MK_Dev #2

If you're only appending a single variable, then push() works just fine. If you need to append another array, use concat():

var ar1 = [1, 2, 3];
var ar2 = [4, 5, 6];

var ar3 = ar1.concat(ar2);

alert(ar1);
alert(ar2);
alert(ar3);

Will spit out:

"1,2,3"
"4,5,6"
"1,2,3,4,5,6"

The concat does not affect ar1 and ar2 unless reassigned, for example:

ar1 = ar1.concat(ar2);
alert(ar1);

Will display:

"1,2,3,4,5,6"

Lots of great info here

answered 8 years ago Jens Roland #3

Some quick benchmarking (each test = 500k appended elements and the results are averages of multiple runs) showed the following:

Firefox 3.6 (Mac):

  • Small arrays: arr[arr.length] = b is faster (300ms vs. 800ms)
  • Large arrays: arr.push(b) is faster (500ms vs. 900ms)

Safari 5.0 (Mac):

  • Small arrays: arr[arr.length] = b is faster (90ms vs. 115ms)
  • Large arrays: arr[arr.length] = b is faster (160ms vs. 185ms)

Google Chrome 6.0 (Mac):

  • Small arrays: No significant difference (and Chrome is FAST! Only ~38ms !!)
  • Large arrays: No significant difference (160ms)

I like the arr.push() syntax better, but I think I'd be better off with the arr[arr.length] Version, at least in raw speed. I'd love to see the results of an IE run though.


My benchmarking loops:

function arrpush_small() {
    var arr1 = [];
    for (a = 0; a < 100; a++)
    {
        arr1 = [];
        for (i = 0; i < 5000; i++)
        {
            arr1.push('elem' + i);
        }
    }
}

function arrlen_small() {
    var arr2 = [];
    for (b = 0; b < 100; b++)
    {
        arr2 = [];
        for (j = 0; j < 5000; j++)
        {
            arr2[arr2.length] = 'elem' + j;
        }
    }
}


function arrpush_large() {
    var arr1 = [];
    for (i = 0; i < 500000; i++)
    {
        arr1.push('elem' + i);
    }
}

function arrlen_large() {
    var arr2 = [];
    for (j = 0; j < 500000; j++)
    {
        arr2[arr2.length] = 'elem' + j;
    }
}

answered 7 years ago rjmunro #4

If arr is an array, and val is the value you wish to add use:

arr.push(val);

E.g.

arr = ['a', 'b', 'c'];
arr.push('d');
console.log(arr);

will log:

['a', 'b', 'c', 'd']

answered 7 years ago Mαzen #5

Use concat:

a = [1, 2, 3];
b = [3, 4, 5];
a = a.concat(b);

a now contains all the elements, [1, 2, 3, 3, 4, 5].

Reference: https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/concat

answered 6 years ago yoel halb #6

If you know the highest index (such as stored in a variable "i") then you can do

myArray[i + 1] = someValue;

However if you don't know then you can either use

myArray.push(someValue);

as other answers suggested, or you can use

myArray[myArray.length] = someValue; 

Note that the array is zero based so .length return the highest index plus one.

Also note that you don't have to add in order and you can actually skip values, as in

myArray[myArray.length + 1000] = someValue;

In which case the values in between will have a value of undefined.

It is therefore a good practice when looping through a JavaScript to verify that a value actually exists at that point.

This can be done by something like the following:

if(myArray[i] === "undefined"){ continue; }

if you are certain that you don't have any zeros in the array then you can just do:

if(!myArray[i]){ continue; }

Of course make sure in this case that you don't use as the condition myArray[i] (as some people over the internet suggest based on the end that as soon as i is greater then the highest index it will return undefined which evaluates to false)

answered 6 years ago Omnimike #7

I think it's worth mentioning that push can be called with multiple arguments, which will be appended to the array in order. For example:

var arr = ['first'];
arr.push('second', 'third');
console.log(arr); // ['first', 'second', 'third']

As a result of this you can use push.apply to append an array to another array like so:

arr.push.apply(arr, ['forth', 'fifth']);
console.log(arr); // ['first', 'second', 'third', 'forth', 'fifth']

Annotated ES5 has more info on exactly what push and apply do.

2016 update: with spread, you don't need that apply anymore, like:

arr.push(...['fourth', 'fifth']);
console.log(arr) // ['first', 'second', 'third', 'fourth', 'fifth']

answered 4 years ago Fizer Khan #8

You can use push and apply function to append two arrays.

var array1 = [11, 32, 75];
var array2 = [99, 67, 34];

Array.prototype.push.apply(array1, array2);

It will append array2 to array1. Now array1 contains [11, 32, 75, 99, 67, 34]. This code is much simpler than writing for loops to copy each and every items in the array.

answered 4 years ago Pawan Singh #9

If you want to append two arrays -

var a = ['a', 'b'];
var b = ['c', 'd'];

then you could use:

var c = a.concat(b);

And if you want to add record g to array (var a=[]) then you could use:

a.push('g');

answered 4 years ago hawkeye126 #10

Let the array length property do the work:

myarray[myarray.length] = 'new element value added to the end of the array';

myarray.length returns the number of strings in the array. JS is zero based so the next element key of the array will be the current length of the array. EX:

var myarray = [0, 1, 2, 3],
    myarrayLength = myarray.length; //myarrayLength is set to 4

answered 3 years ago Maarten Peels #11

The push() method adds new items to the end of an array, and returns the new length. Example:

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.push("Kiwi");

// The result of fruits will be:
Banana, Orange, Apple, Mango, Kiwi

The exact answer to your question is already answered, but let's look at some other ways to add items to an array.

The unshift() method adds new items to the beginning of an array, and returns the new length. Example:

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.unshift("Lemon", "Pineapple");

// The result of fruits will be:
Lemon, Pineapple, Banana, Orange, Apple, Mango

And lastly, the concat() method is used to join two or more arrays. Example:

var fruits = ["Banana", "Orange"];
var moreFruits = ["Apple", "Mango", "Lemon"];
var allFruits = fruits.concat(moreFruits);

// The values of the children array will be:
Banana, Orange, Apple, Mango, Lemon

answered 3 years ago CodingIntrigue #12

With the new ES6 spread operator, joining two arrays using push becomes even easier:

var arr = [1, 2, 3, 4, 5];
var arr2 = [6, 7, 8, 9, 10];
arr.push(...arr2);
console.log(arr); // [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

This adds the contents of arr2 onto the end of arr.

Babel REPL Example

answered 3 years ago Danil Gaponov #13

Just want to add a snippet for non-destructive addition of an element.

var newArr = oldArr.concat([newEl]);

answered 3 years ago Karl #14

concat(), of course, can be used with 2 dimensional arrays as well. No looping required.

var a = [ [1, 2], [3, 4] ];

var b = [ ["a", "b"], ["c", "d"] ];

b = b.concat(a);

alert(b[2][1]); // result 2

answered 3 years ago Zhenyang Hua #15

Javascript with ECMAScript 5 standard which is supported by most browsers now, you can use apply() to append array1 to array2.

var array1 = [3, 4, 5];
var array2 = [1, 2];

Array.prototype.push.apply(array2, array1);

console.log(array2); // [1, 2, 3, 4, 5]

Javascript with ECMAScript 6 standard which is supported by Chrome and FF and IE Edge, you can use the spread operator:

"use strict";
let array1 = [3, 4, 5];
let array2 = [1, 2];

array2.push(...array1);

console.log(array2); // [1, 2, 3, 4, 5]

The spread operator will replace array2.push(...array1); with array2.push(3, 4, 5); when the browser is thinking the logic.

Bonus point

If you'd like to create another variable to store all the items from both array, you can do this:

ES5 var combinedArray = array1.concat(array2);

ES6 const combinedArray = [...array1, ...array2]

The spread operator (...) is to spread out all items from a collection.

answered 2 years ago Satyapriya Mishra #16

If you want to append a single value into an array simply use the push method... It will add a new element at the end of the array. But if you intend to add multiple elements then store the elements in a new array and concat the second array with the first array...either way you wish.

arr=['a','b','c'];
arr.push('d');
//now print the array in console.log and it will contain 'a','b','c','d' as elements.

answered 2 years ago Emil Reña Enriquez #17

if you want to combine 2 arrays without the duplicate you may try the code below

array_merge = function (arr1, arr2) {
  return arr1.concat(arr2.filter(function(item){
    return arr1.indexOf(item) < 0;
  }))
}

usage:

array1 = ['1', '2', '3']
array2 = ['2', '3', '4', '5']
combined_array = array_merge(array1, array2)

Output: [1,2,3,4,5]

answered 2 years ago JmLavoier #18

If you are using the ES6 you can use spread operator to do it.

var arr = [
    "apple",
    "banana",
    "cherry"
];

var arr2 = [
    "dragonfruit",
    "elderberry",
    "fig"
];

arr.push(...arr2);

answered 2 years ago Inconnu #19

There are a couple of ways to append an array in JavaScript:

1) The push() method adds one or more elements to the end of an array and returns the new length of the array.

var a = [1, 2, 3];
a.push(4, 5);
console.log(a);

Output:

[1, 2, 3, 4, 5]

2) The unshift() method adds one or more elements to the beginning of an array and returns the new length of the array:

var a = [1, 2, 3];
a.unshift(4, 5);
console.log(a); 

Output:

[4, 5, 1, 2, 3]

3) 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.

var arr1 = ["a", "b", "c"];
var arr2 = ["d", "e", "f"];
var arr3 = arr1.concat(arr2);
console.log(arr3);

Output:

[ "a", "b", "c", "d", "e", "f" ]

4) You can use the array's .length property to add an element to the end of the array:

var ar = ['one', 'two', 'three'];
ar[ar.length] = 'four';
console.log( ar ); 

Output:

 ["one", "two", "three", "four"]

5) The splice() method changes the content of an array by removing existing elements and/or adding new elements:

var myFish = ["angel", "clown", "mandarin", "surgeon"];
myFish.splice(4, 0, "nemo");
//array.splice(start, deleteCount, item1, item2, ...)
console.log(myFish);

Output:

["angel", "clown", "mandarin", "surgeon","nemo"]

6) You can also add a new element to an array simply by specifying a new index and assigning a value:

var ar = ['one', 'two', 'three'];
ar[3] = 'four'; // add new element to ar
console.log(ar);

Output:

["one", "two","three","four"]

answered 1 year ago José Antonio Postigo #20

Now, you can take advantage of ES6 syntax and just do:

let array = [1, 2];
console.log([...array, 3]);

keeping the original array immutable.

answered 1 year ago Alireza #21

We don't have append function for Array in javascript, but we have push and unshift, imagine you have the array below:

var arr = [1, 2, 3, 4, 5];

and we like append a value to this array, we can do, arr.push(6) and it will add 6 to the end of the array:

arr.push(6); // return [1, 2, 3, 4, 5, 6];

also we can use unshift, look at how we can apply this:

arr.unshift(0); //return [0, 1, 2, 3, 4, 5];

They are main functions to add or append new values to the arrays.

answered 1 year ago Jack #22

You .push() that value in. Example: array.push(value);

answered 8 months ago Hoque MD Zahidul #23

you can do it using new javascript Es 6 feature :

// initialize array

var arr = [
    "Hi",
    "Hello",
    "Bangladesh"
];

// append new value to the array

arr= [...arr , "Feni"];

// or you can put a variable value

var testValue = "Cool";

arr = [...arr , testValue ];

console.log(arr); 

// final output  [ 'Hi', 'Hello', 'Bangladesh', 'Feni', 'Cool' ]

answered 8 months ago George Bailey #24

Using the method push() will append an item to an array. See the example below.

 array=['a','b','c'];
 array.push('d')
 console.log(array);  

answered 5 months ago Sanu Uthaiah Bollera #25

You can use push method.

Array.prototype.append = function(destArray){
     destArray = destArray || [];
     this.push.call(this,...destArray);
     return this;
}
var arr = [1,2,5,67];
var arr1 = [7,4,7,8];
console.log(arr.append(arr1));// [7, 4, 7, 8, 1, 4, 5, 67, 7]
console.log(arr.append("Hola"))//[1, 2, 5, 67, 7, 4, 7, 8, "H", "o", "l", "a"]

answered 4 weeks ago Lior Elrom #26

Append a value to an array

Since Array.prototype.push adds one or more elements to the end of an array and returns the new length of the array, sometimes we want just to get the new up-to-date array so we can do something like so:

const arr = [1, 2, 3];
const val = 4;

arr.concat([val]); // [1, 2, 3, 4]

Or just:

[...arr, val] // [1, 2, 3, 4]

answered 4 weeks ago Harunur Rashid #27

push() adds a new element to the end of an array.
pop() removes an element from the end of an array.

To append an object (such as a string or number) to an array use -
array.push(toAppend);

answered 5 days ago Flavio Copes #28

Append a single item

To append a single item to an array, use the push() method provided by the Array object:

const fruits = ['banana', 'pear', 'apple']
fruits.push('mango')
console.log(fruits)

push() mutates the original array.

To create a new array instead, use the concat() Array method:

const fruits = ['banana', 'pear', 'apple']
const allfruits = fruits.concat('mango')
console.log(allfruits)

Notice that concat() does not actually add an item to the array, but creates a new array, which you can assign to another variable, or reassign to the original array (declaring it as let, as you cannot reassign a const):

const fruits = ['banana', 'pear', 'apple']
const allfruits = fruits.concat('mango')
console.log(allfruits)

js let fruits = ['banana', 'pear', 'apple'] fruits = fruits.concat('mango')

Append multiple items

To append a multiple item to an array, you can use push() by calling it with multiple arguments:

const fruits = ['banana', 'pear', 'apple']
fruits.push('mango', 'melon', 'avocado')
console.log(fruits)

You can also use the concat() method you saw before, passing a list of items separated by a comma:

const fruits = ['banana', 'pear', 'apple']
const allfruits = fruits.concat('mango', 'melon', 'avocado')
console.log(allfruits)

or an array:

const fruits = ['banana', 'pear', 'apple']
const allfruits = fruits.concat(['mango', 'melon', 'avocado'])
console.log(allfruits)

Remember that as described previously this method does not mutate the original array, but it returns a new array.

Originally posted at https://flaviocopes.com/how-to-append-item-to-array/

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