![]() ![]() There are several different ways to make a copy of an array, including: om, the spread operator, or calling the slice function with no arguments. The way to work around this has been to copy the array first, then mutate it. The React docs have a whole page explaining how to update arrays in state because of this. ![]() Instead you need to copy the array first, then mutate the copy and set that as the new state. You can't mutate an array and then try to set it as a new state because the array itself is the same object and this won't trigger a new render. One of the best known issues with array methods that mutate the array is when you use them in a React component. => Ĭonsole.log(Object.is(languages, reversed)) Īs you can see, the original array was reversed and even though we assigned the result of reversing the array to a new variable, both variables simply point to the same array. When you perform an operation on an object that mutates it, that is a side effect and can cause unexpected behaviour elsewhere in your system.Īs an example, this is what happens when you reverse an array. Other methods like concat, map, and filter create a copy of the array and then operate on the copy. Methods like sort, reverse, and splice change the array in place. The Array object has always had some oddities. Read on to learn the difference and how to start using them in your projects. ![]() ![]() The methods toSorted, toReversed, toSpliced, and with allow you to perform operations on arrays by without changing the data in place, but by making a copy and changing that copy. It includes some new methods on the Array object that will help make our JavaScript programs more predictable and maintainable. The ECMAScript 2023 specification has been recently finalised. ![]()
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