The outcome from employing array.splice was totally unforeseen

Question

The outcome from employing array.splice was totally unforeseen

I devised a JavaScript method to select items from an array and display the final item. However, I noticed that this process was inadvertently removing items from the original array.

Here is the function:

function oneRemaining(arr) {
    tmp = arr;
    while (tmp.length > 1) {
        tmp.splice(~~(Math.random() * tmp.length), 1);
    }
    return tmp[0];
}

After executing this function, the initial array should remain unchanged because it was not supposed to be modified. Unfortunately, when I tested it in the console, only one item was left in the array.

What could be causing the input array to be altered?

javascript arrays

Answer 1

Answer №1

The reason your array is changing is because of the following factors:

Instead of creating a copy or clone, you created a reference which means you are manipulating the original array.
Splice directly modifies the underlying array, making it one of the few methods that do so (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/splice)

To prevent this issue, consider replacing your second line with:

tmp = arr.concat([])

I hope this information proves to be useful for you.

Answer 2

The reason your array is changing is because of the following factors:

Instead of creating a copy or clone, you created a reference which means you are manipulating the original array.
Splice directly modifies the underlying array, making it one of the few methods that do so (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/splice)

To prevent this issue, consider replacing your second line with:

tmp = arr.concat([])

I hope this information proves to be useful for you.

Answer 3

Answer №2

The transformation is occurring due to the fact that tmp points to arr rather than being a duplicate of it. Any modifications made to a referenced object will also affect the original.

Answer 4

The transformation is occurring due to the fact that tmp points to arr rather than being a duplicate of it. Any modifications made to a referenced object will also affect the original.

Answer 5

Answer №3

Arrays in JavaScript are considered reference types, meaning that when you assign a variable to an array, you are actually assigning a reference to that array rather than making a copy of it. This means that any changes made to the variable will affect the original array in memory.

tmp = arr;

If you want to create a true copy of your input array, you can use the .slice(0) method on the array.

(Also, don't forget to include the var keyword before declaring the tmp variable, unless you intend for it to be global.)

Answer 6

Arrays in JavaScript are considered reference types, meaning that when you assign a variable to an array, you are actually assigning a reference to that array rather than making a copy of it. This means that any changes made to the variable will affect the original array in memory.

tmp = arr;

If you want to create a true copy of your input array, you can use the .slice(0) method on the array.

(Also, don't forget to include the var keyword before declaring the tmp variable, unless you intend for it to be global.)

The outcome from employing array.splice was totally unforeseen

Answer №1

Answer №2

Answer №3

Similar questions

Using Angular $resource to store an object with arrays

Cannot find the appended element in an AJAX call using jQuery

Leetcode problem 833 deals with replacing strings based on their index positions

What is the best way to send a variable to inline javascript via the EJS templating engine?

Modify the javascript addEventListener to use 'scroll' instead of 'wheel'

Why was the 'Symbol' type introduced in ECMA-262-v6 and what purpose does it serve?

Implementing complex routing with Express.js on top of Node.js

Looking to display outcomes on a separate line every time you click? Currently developing a project involving Rock, Paper, Scissors

Error: cannot assign 'int*' to 'int [0]', the types are incompatible and will not compile

I just can't seem to grasp pointers in C no matter how hard I try

Is it possible to attach React Components to Elements without using JSX?

How come WhatsApp is not recognizing my og:tags correctly?

What is the maximum allowable size for scripts with the type text/json?

Hide modal once form has been successfully submitted

Tracking changes in an email input using Angular's $watch functionality

Troubleshooting RangeError in AngularJS $routeParams: Exceeding maximum call stack size

Why doesn't Bootstrap have access to the tab view obtained on _Layout.cshtml when it is clicked?

display the returned value in the database function before rendering response

Guide to configuring browserify

Thumbnail Carousel Caption in Bootstrap 3