Remove last item from array

Question

I have the following array.

var arr = [1,0,2];

I would like to remove the last element i.e. 2.

I used arr.slice(-1); but it doesn't remove the value.

Answer 1

You can do this using .slice() method like:

var arr = [1,0,2]
arr.slice(0, -1);    // returns [1,0]

Here is a demo:

var arr = [1, 0, 2];
var newArr = arr.slice(0, -1);    // returns [1,0]

console.log(newArr);
$('#div1').text('[' + arr + ']');
$('#div2').text('[' + newArr + ']');

<script src="http://code.jquery.com/jquery.min.js"></script>
<b>Original Array    : </b>
<div id="div1"></div>
<br/>
<b>After slice(0, -1): </b>
<div id="div2"></div>

instead of doing:

arr.slice(-1);   // returns [2]

Here is a demo:

var arr = [1, 0, 2];
var newArr = arr.slice(-1);    // returns [2]

console.log(newArr);
$('#div1').text('[' + arr + ']');
$('#div2').text('[' + newArr + ']');

<script src="http://code.jquery.com/jquery.min.js"></script>
<b>Original Array    : </b>
<div id="div1"></div>
<br/>
<b>After slice(-1): </b>
<div id="div2"></div>

Explanation:

Now the basic syntax of Array.prototype.slice() or in short slice() method is:

arr.slice([begin[, end]])

Here,

the begin parameter is zero-based index at which extraction from an array starts. So, lets say based on above example if we do something like

arr.slice(0)    // returns [1,0,2]

it would return all the array elements from start of sequence from position 0 and that is [1,0,2]. Similarly, if we do

arr.slice(1)    // returns [0,2]

it would return [0,2] since 0 is at position 1 here and everything after that. Now, in your case you have passed a negative index i.e., -1 as the begin parameter, which indicates an offset from the end of the sequence. So, slice(-1) in your case extracts the last one array element in the sequence and that is 2 (as we have already seen in the above demo).

Now, let's talk about the end parameter in the slice() method syntax here. It is again a zero-based index at which extraction from an array ends. So, lets say we have an array like:

var arr = [1, 0, 2, 5, 3, 9];

and we want to get just the 2,5,3 elements in the array. Now, position of 2 from start of the sequence is 2 and for last element 3 it is 4. We will need to end the extraction here a position 5, as we need to get the element before that position. So, we will simply implement slice() method here like

arr.slice(2, 5)    // returns [2,5,3]

In your case, we have implemented -1 as the end parameter, so our code is like

arr.slice(0, -1)   // returns [1,0]

As a negative index, end indicates an offset from the end of the sequence. So, slice(0,-1) extracts the first element through the second-to-last element in the sequence. So, we get the desired output. We can also do like

arr.slice(0, 2)    // returns [1,0]

we will get the same output. But, I have used -1 here as its easier to implement even for a long array like

[0,2,3,1,2,9,3,6,3,9,1,0,2,9,0,1,1,2,3,4,7,9,1]

If you just want to remove the last element, you don't want to sit & calculate the position of last 9 here and the do like arr.slice(0, 22). You can then simply implement the negative index logic here & do

arr.slice(0, -1) // same result as arr.slice(0, 22)

Answer 2

Array.prototype.pop() by JavaScript convention.

let fruit = ['apple', 'orange', 'banana', 'tomato'];
let popped = fruit.pop();

console.log(popped); // "tomato"
console.log(fruit); // ["apple", "orange", "banana"]

Answer 3

var arr = [1,0,2];
arr.length--; 

removes the last element, but you might need to check if arr.length > 0 first.

Answer 4

If you're looking for a one-liner that doesn't require you to initialize multiple variables:

var arr = [1,0,2];

arr = arr.filter((_,i,a) => i !== (a.length-1));

Explanation: We're using the Array Filter Method which takes in 3 callbacks:

1. element (_): the current element during the iteration
2. index (i): the index of the element iteration
3. array (a): the array that is being used for the filter

So we just skip the element if it's the last element in the array that is being used.

The _ is just a placeholder because we're not actually using it.

Answer 5

var arr = [ 0, 1, 2, 3, 4, 5, 6, 7 ];

// using slice
arr = arr.slice(0, -1);
console.log('arr : ', arr);

// using splice
arr.splice(-1);
console.log('arr : ', arr);

// using pop
arr.pop();
console.log('arr : ', arr);

// using shift and reverse
arr.reverse().shift()
arr.reverse();
console.log('arr : ', arr);

// using spread Operator and reverse
const [, ...exceptLast] = arr.reverse();
arr = exceptLast.reverse();
console.log('arr : ', arr);

// removing last index
arr.length -= 1;
console.log('arr : ', arr);

Answer 6

You would need to do this since slice doesn't alter the original array.

arr = arr.slice(0, -1);

If you want to alter the original array you can use splice:

arr.splice(-1, 1);

or pop:

arr.pop();

Answer 7

I got the best answer!

var array = [1, 2, 3, 4]
array.length = array.length - 1

console.log(array)
> [1, 2, 3]

Honestly JS is a meme at this point.

PS: This affects the variable and any of its references, if you want to not affect any of the variable's references you can do:

var array = [1, 2, 3, 4]
var modifiedArray = Array.from(array)
modifiedArray .length = modifiedArray .length - 1

console.log(modifiedArray )
> [1, 2, 3]

Answer 8

Use splice(startPosition, deleteCount)

array.splice(-1)

var array = ['abc','def','ghi','123'];
var removed = array.splice(-1);  //last item
console.log( 'array:', array );
console.log( 'removed:', removed );

Answer 9

It's worth noting that slice will both return a new array, whereas .pop() and .splice() will mutate the existing array.

If you like handling collections of data with a chained command style, you will really want to stick with slice for something like this.

For example:

myArray = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

var newArrayOfThings = myArray
  .filter(x => x > 5)              // only bigly things
  .slice(0, -1)                       // get rid of the last item ! slice(-1) will give first element
  .map(x => `The number is: ${x}`);// map to a set of strings

It can require a lot more messing about, and variable management, to do the same kind of thing with "pop", since unlike map, filter, etc, you don't get a new array back.

It's the same kind of thing with push, which adds an item to the end of an array. You might be better off with concat since that lets you keep the flow going.

myArray = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

var newArrayOfThings = myArray
  .filter(x => x > 5)              // only bigly things
  .slice(-1)                       // get rid of the "10"
  .concat([100])                   // note with concat, you must pass an array
  .map(x => `The number is: ${x}`) // map to a set of strings
  

Answer 10

learn by example:

let array_1 = [1,2,3,4];
let array_2 = [1,2,3,4];
let array_3 = [1,2,3,4];
let array_4 = [1,2,3,4];

array_1.splice(-1,1)  // returned --> [4]      array_1 = [1,2,3]
array_2.slice(0,-1);  // returned --> [1,2,3]  array_2 = [1,2,3,4]
array_3.pop();        // returned --> 4        array_3 = [1,2,3]
array_4.shift();      // returned --> 1        array_4 = [2,3,4]

Answer 11

// Setup
var myArray = [["John", 23], ["cat", 2]];

// Only change code below this line
var removedFromMyArray;
removedFromMyArray = myArray.pop()

Answer 12

Simply arr.splice(-1) will do.

Answer 13

Using the spread operator:

const a = [1,2,3]
const [, ...rest] = a.reverse();
const withoutLast = rest.reverse();
console.log(withoutLast)

Answer 14

Just use the following for your use case:

var arr = [1,2,3,4];
arr.pop() //returns 4 as the value
arr // value 4 is removed from the **arr** array variable

Just a note. When you execute pop() function even though the line returns the popped item the original array is effected and the popped element is removed.

Answer 15

Another approach is to filter based on index:

arr.filter((element, index) => index < arr.length - 1);

Note: filter() creates new array, doesn't change existing one.

Answer 16

If you want to remove n item from end of array in javascript, you can easily use:

arr.splice(-n, n);

Answer 17

2019 ECMA5 Solution:

const new_arr = arr.reduce((d, i, idx, l) => idx < l.length - 1 ? [...d, i] : d, [])

Non destructive, generic, one-liner and only requires a copy & paste at the end of your array.

Answer 18

I would consider .pop() to be the most 'correct' solution, however, sometimes it might not work since you need to use array without the last element right there...

In such a case you might want to use the following, it will return [1,2,3]

var arr = [1,2,3,4];
console.log(arr.splice(0,arr.length-1));

while .pop() would return 4:

var arr = [1,2,3,4];
console.log(arr.pop());

which might not be desirable...

Hope this saves you some time.

Answer 19

var a = [1,2,3,4,5,6]; 
console.log(a.reverse().slice(1).reverse());
//Array(5) [ 1, 2, 3, 4, 5 ]

Answer 20

You can do it in two way using splice():

1. arr.splice(-1,1)
2. arr.splice(arr.length-1,1)

splice(position_to_start_deleting, how_many_data_to_delete) takes two parameter.

position_to_start_deleting : The zero based index from where to start deleting. how_many_data_to_delete : From indicated index, how many consecutive data should be deleted.

You can also remove the last element using pop() as pop() removes the last element from some array.
Use arr.pop()

Answer 21

With Lodash you can use dropRight, if you don't care to know which elements were removed:

_.dropRight([1, 2, 3])
// => [1, 2]

_.dropRight([1, 2, 3], 2);
// => [1]

Answer 22

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

stack.reverse().shift();

stack.push(0);

Output will be: Array[0,1,2,3,4,5]. This will allow you to keep the same amount of array elements as you push a new value in.

Answer 23

This method is more helpful to delete and store the last element of an array.

var sampleArray = [1,2,3,4];// Declaring the array
var lastElement = sampleArray.pop();//this command will remove the last element of `sampleArray` and stores in a variable called `lastElement` so that you can use it if required.

Now the results are:

console.log(sampleArray); //This will give you [1,2,3]
console.log(lastElement); //this will give you 4

Answer 24

This is good way to remove last item :

if (arr != null && arr != undefined && arr.length > 0) {
      arr.splice(arr.length - 1, 1);
}

Detail of splice as following:

splice(startIndex, number of splice)

Answer 25

say you have var arr = [1,0,2]

arr.splice(-1,1) will return to you array [1,0]; while arr.slice(-1,1) will return to you array [2];

Answer 26

splice(index,howmany) - This solution sounds good. But This howmany will work only for the positive array index. To remove last two items or three items use the index itself.

For example, splice(-2) to remove last two items. splice(-3) for removing last three items.

Answer 27

There is a function for that, explanation here:

arr.pop();

Answer 28

arr.slice(-1) will return a copy of the last element of the array, but leaves the original array unmodified.

To remove the last n elements from an array, use arr.splice(-n) (note the "p" in "splice"). The return value will be a new array containing the removed elements.

Simpler yet, for n == 1, use val = arr.pop()

Answer 29

You could simply use, arr.pop()

This removes the last entry of the array.

var arr = [1,0,2]; 
var popped = arr.pop();//Now arr = [1,0] & popped = 2