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Hopefully this post has helped you understand the difference between JavaScript array's slice and splice methods and how they work. const array = Ĭonsole.log(array) // Conclusion This means that you can set count to 0 with additional parameters to add to the array. Every parameter after the count parameter will be added to the array. You can pass an unlimited number of parameters to the splice method. When you provide both the start and count parameters, it will remove count number of elements, starting at the start index. When you only provide the start parameter, it will remove all elements from that index to the end of the array. The splice method will directly modified the array, essentially adding or removing elements from it using the optional start and count parameters.

When you provide both the start and end parameters, it will return the elements between those two indexes. The start parameter can be negative to start at the end of the array. The start parameter is zero-based so the first element is at index 0. If you provide the start parameter, it will start at that index and go until the end of the array. They're both optional so if you leave both blank, it will return the entire array. The slice method will take an array and return a new array with the elements specified by the optional start and end parameters. Sorting methods have an O (n log n) which is worse than O (n).

Although splice can remove/add elements from anywhere in the array it has an O (n) because, in the worst case scenario, all array inputs would be impacted. The difference between slice and splice is that slice is immutable whereas splice will mutate the array. Splice is a method that, changes the contents of an array by removing the existing elements and/or adding new elements (MDN). So to insert 'c', you call splice() with a deleteCount of 0 and 'c' as the third parameter.In this post, we'll learn the difference between the JavaScript array methods slice() and splice() and when it's appropriate to use one over the other. Every parameter to splice() after the deleteCount parameter is treated as an element to add to the array at the startIndex. The splice() function is the only native array function that lets you add elements to the middle of an array.įor example, suppose you have an array and you want to add 'c' after 'b'. JavaScript arrays have a push() function that lets you add elements to the end of the array, and an unshift() function that lets you add elements to the beginning of the array. The splice() function also lets you add elements to the middle of the array. On the other hand, `splice()` modifies the array in place.Īrr2 = arr // false Adding Elements to the Middle `arr` still has 'c', because `filter()` doesn't modify the array // in place. Remove 1 element starting at index 2 const arr2 = arr.filter( ( v, i) => i != 2) This means filter() is the better choice for applications that rely on immutability, like React apps. The key difference between these two approaches is that filter() creates a new array. You may see JavaScript projects use filter() instead of splice() to remove elements from an array. The deleteCount parameter tells splice() how many elements to delete. The start parameter tells splice() where to start modifying the array. The first 2 parameters to splice() are called start and deleteCount. Here's how you would remove 'c' using splice(): const arr = The splice() function is the only native array function that lets you remove elements from the middle of the array without creating a new array. It is most commonly used to remove elements from an array, but it can also be used to add elements to the middle of an array. The Array#splice() function lets you modify an array in-place by adding and removing elements.