It is “frowned upon” to modify javascript primitive functions like Array and String. You could possibly be overloading an already existing function and trash the object class. There might be an obscure javascript engine that already has clear() and expects it to behave a different way. @thefourtheye The whole point of not modifying global scope is because you won’t know if someone else’s code is already using the name.
- A third way to clear an array is to use .splice().
- This function will return a copy of the array before deleting the entries, which is helpful if you want to do a reassignment before clearing the array.
- Please use caution in deciding how to handle this.
- In this solution, the splice() method removed all the elements of the a array and returned the removed elements as an array.
I tried it on most of browsers, like IE, Firefox, Chrome, it is creating new array. If you set length greater than 0 then it will create an array with undefined elements, i.e. it will just hold some memory locations. The original benchmark reused the cleared array so the second iteration was clearing an array that was already empty. Of all the methods of clearing an existing array, methods 2 and 3 are very similar in performance and are a lot faster than method 4. Benchmarks suggest that this has no effect on performance whatsoever.
Table of Contents
The array.length is a built-in JavaScript property that sets or returns the number of items in the array. I also have an alsoWizards variable, and I set its value to the wizards array. This comes with the downside of creating a new array and leaving the old one for the garbage collector.
So, inside your application’s/library’s IIFE, do function clear , then clear arrays with clear instead of arr.clear(). This is the fastest way to clear an array, but requires that you don’t have references to the original array elsewhere in your code. Setting the length to zero will empty the existing array.
It also works when using “strict mode” in ECMAScript 5 because the length property of an array is a read/write property. Use this method if you only reference the array by its original variable arr. The original array will remain unchanged if you have referenced this array from another variable or property.
JavaScript Fundamentals
The simplest solution is to assign the array’s length to the value of 0. You can reassign a new value to a variable that initially has a non-empty array assigned to it. With a length of 0, every value in the array gets removed, and the array becomes empty. The length property of an array is readable and writeable. The following shows you several methods to make an array empty.
Garbage collection is an optimized process in nowadays Node.js runtimes. It won’t create much headache for you as a developer. A common How to install add-apt-repository in Ubuntu Debian approach to resetting an array is to re-declare it with an empty array – replacing the current value of the array with an empty one.
JavaScript Objects
She has more than 20 years of experience creating technical documentation and leading support teams at major web hosting and software companies. Nicole also holds an MFA in Creative Writing from Portland State University and teaches composition, fiction-writing, and zine-making at various institutions. If I reassign the value of wizards, the alsoWizards variable still points to the original array that was assigned to it. But sometimes, you have an array that’s assigned by reference, and you want to keep them linked. The most common way to do this is to reassign the value of the wizards variable to an empty array ([]). We can use this method inside a loop and iterate until the length of the array is greater than zero.
Currently, I’m building desktop and web-based solutions with NodeJS and PHP hosted on Linux infrastructure. Visit my blog or find me on Twitter to see what I’m up to. This method can also work in case of “strict mode” in ECMAScript 5 because the length property is a read/write property.
Return value
This is perfect if you don’t have references to the original array A anywhere else because this actually creates a brand new array. You should be careful with this method because if you have referenced this array from another variable or property, the original array will remain unchanged. Only use this if you only reference the array by its original variable A. You can reset array values or clear the values very easily in PHP. There are two methods to reset the array which are discussed further in this article.
PHP Advanced
Please use caution in deciding how to handle this. @daghan, it’s not at all clear what you’re trying to say. B holds a reference to the old array even after a is assigned a new one. This solution is not very succinct, and it is also the slowest solution, contrary to earlier benchmarks referenced in the original answer.
Using this approach, you don’t leave work for the garbage collector, but possibly affect referenced arrays and reset them as well. All JavaScript runtimes (Browser, Node.js) are optimized for the operation to set the array length to zero. Setting it to 0 means, we are emptying the array. It removes each item in the array, which does hit other references.
If you want to avoid mutating the arrays in place for immutability, you can overwrite the array with an empty array []. In this article, How to Become a Game Developer in 2022? Step-by-Step Guide I’ll show and explain two ways to clear an array. Why developer experience is the key to better software, straight from the…
Also, this method is the fastest & easiest way to clear an array. This will remove all elements from the array and will actually clean the original array. This is perfect if you don’t have any references from other places to the original arr. If you do, those references won’t be updated and those places will continue to use the old array.
This has been a hot topic and the cause of a lot of controversy. There are actually many correct answers and because this answer has been marked as the accepted answer for a very long time, I will include all of the methods here. To use the splice() method, pass the first argument as 0 and the array length as the second parameter. We have defined an array dark with three elements and then emptied that array by substituting with . This is the fastest way to empty an array in Javascript. This article was co-authored by wikiHow staff writer, Nicole Levine, MFA. Nicole Levine is a Technology Writer and Editor for wikiHow.
This should give you a more definite answer for the browser of your choice. A lot of answers here are old and I wouldn’t rely on them but rather test as in @tanguy_k’s answer above. This will return the copy of the original elements, which may be handy for some 7 Best Online Course to Learn Programming & Coding in 2022 by javinpaul Javarevisited scenarios but will remove all items from the array and clean the original array. The fastest way to clear or empty an array in Javascript is by substituting an existing array with a new empty array. To clear anarray in Javascript, set an array length prop to 0.