¿Cómo se puede prevenir una mutación de matriz?

How can an array mutation be prevented?

Avoid Array Mutation in JavaScript

1. Generate Arrays. Array(5).fill(0); // [0, 0, 0, 0, 0] Array.from(Array(5), (_, index) => 2 + index); // [2, 3, 4, 5, 6]
2. Checking for Array Type. const array = [‘a’, ‘b’]; Array.isArray(array); // true, also works through iframes array instanceof Array; // true.
3. Shallow Copy / Clone Arrays.

It’s easy to avoid mutating objects by providing an empty object in the target parameter. MDN always having our back for the breakdown: Properties in the target object are overwritten by properties in the sources if they have the same key.

There are two ways to add new items to an array without mutating the original array. First, there is array. concat() . The second way to add to an array without mutating the original involves using JavaScript’s spread operator.

If you want to mutate the original array, you can use Array#forEach function. Array#map creates a new array of the created items and returns that. After you need to assign the returned result. You can mutate the objects directly iterating with map.

Mutation is basically changing the array itself instead of returning a new array with the new changes.

Declaring a variable with const doesn’t make it immutable, it prevents you from assigning another value to it. When you declare an object with const , you’re still allowed to mutate the object.

push allows us to push elements to the end of an array. This method does not return a new copy, rather mutates the original array by adding a new element and returns the new length property of the object upon which the method was called. There’s also Array.

splice() The . splice() method is powerful, as it can take as many arguments as you want and mutate the array by adding and/or replacing item(s) within the array. slice() method produces a new array and hence does NOT mutate the original array.

Directly setting the array value at index works, but this is a mutation. If we add a deepFreeze call, it’s not going to work anymore, so how do we replace a single value in the array without mutating it?

There are two ways to add new items to an array without mutating the original array. First, there is array.concat (). The second way to add to an array without mutating the original involves using JavaScript’s spread operator. The spread operator is three dots ( …) preceding an array.

In this lesson, you learned how to use the concat method or the spread operator, and the slice method to add, remove, and change items in arrays without mutating them, and how to protect yourself with deepFreeze from mutation in your tests. Is there a library of non-mutative array methods?

Now my attempt to push does not work. It cannot add a new property to a frozen object. Instead of push, I’m going to use the concat method, which does not modify the original array. Now the tests pass without mutations, and I can also use the new ES6 erase spread operator to write the same code in a more concise way.